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Redlin, Margarete; Gries, Thomas; Meierrieks, Daniel
Conference Paper
Oppressive Governments, US Closeness, and AntiUS Terrorism
Beiträge zur Jahrestagung des Vereins für Socialpolitik 2014: Evidenzbasierte
Wirtschaftspolitik - Session: Causes of Islamistic and Anti-American Terrorism, No. G08-V1
Provided in Cooperation with:
Verein für Socialpolitik / German Economic Association
Suggested Citation: Redlin, Margarete; Gries, Thomas; Meierrieks, Daniel (2014) : Oppressive
Governments, US Closeness, and Anti-US Terrorism, Beiträge zur Jahrestagung des
Vereins für Socialpolitik 2014: Evidenzbasierte Wirtschaftspolitik - Session: Causes of
Islamistic and Anti-American Terrorism, No. G08-V1, ZBW - Deutsche Zentralbibliothek für
Wirtschaftswissenschaften, Leibniz-Informationszentrum Wirtschaft, Kiel und Hamburg
This Version is available at:
http://hdl.handle.net/10419/100588
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Oppressive Governments, US Closeness and Anti-US Terrorism
(Draft Version, do not cite: 2014-02-28)
Thomas Gries1, Daniel Meierrieks2 and Margarete Redlin3
Abstract
Since the 9/11 attacks more attention has been given to the question why the United States is a
major target for transnational terrorism. What conditions motivate these terrorist activities? Are
there specific characteristics in the terrorists’ home countries that provide a breeding ground for
anti-US terrorism? In particular, we ask whether oppressive and bad governments in these
countries and/or close connections with the US encourage attacks against the US. Oppressive
and bad government behavior, such as human rights violations or poor governance, may provoke
resistance against the authorities, including violent attacks. Attacking the United States instead
of one’s own government may be a promising option, especially if the government’s capacity
seems dependent on US support. In a count data approach we use panel data for 149 countries
from 1981 to 2005. We measure governmental “oppressiveness” using the physical integrity
rights index, and measure a government’s closeness to the US with a range of measures.
Controlling for a variety of variables, our findings indicate that both oppressiveness and US
closeness are important determinants of anti-US terrorism. Furthermore, both effects do not
seem completely independent. Sorting into groups, US closeness seems to relate to more attacks
the greater the oppressiveness of one’s home government’s.
Keywords: anti-US terrorism, international aid, human rights
JEL Classification: F35, F51, F52
1
University of Paderborn, Department of Economics, Center for International Economics. Germany. Ph.:
+49-(0)5251-60-3823, fax: +49-(0)5251-60-3540, e-mail:
[email protected].
2
University of Freiburg, Wilfried Guth Endowed Chair for Constitutional Political Economy and
Competition
Policy,
Germany,
Ph.:
+49-761 203-67651,
fax:
+49-761 203-67653,
e-mail:
[email protected]
3
University of Paderborn, Department of Economics, Center for International Economics. Germany. Ph.:
+49-(0)5251-60-3823, fax: +49-(0)5251-60-3540, e-mail:
[email protected].
1
1 Introduction
The United States are a major target of terrorist groups and the attacks of 9/11 led to worldwide
attention on transnational anti-U.S-terrorism. Even if there is no simple explanation for this
phenomenon, single aspects might be possible to study. Anti-U.S. terrorism is not equally
distributed with respect to terrorists’ country origin. Attacks are prevalently done by persons
from certain countries? Hence, an interesting question is, if specific country characteristics
provide a breeding ground for terrorism directed towards the United States. Furthermore, do
certain economic and political conditions in these countries abet the emergence of anti-U.S.
terrorism? Specifically, oppressive state behavior and violations of basic human rights may lead
to political frustration and in turn may involve violent attacks and terrorism against the ruling
authority. In fact, the US government seems to be aware of this reasoning, as President Obama
argued “when the United States stands up for human rights, by example at home and by effort
abroad … we also strengthen our security and well being, because the abuse of human rights can
feed many of the global dangers that we confront -- from armed conflict and humanitarian crises,
to corruption and the spread of ideologies that promote hatred and violence.” (Barak Obama 10th
December, 2008).
Moreover, when governments enjoy international support the international supporter is often
regarded as ally. Hence, if the local authority were a repressive violent regime and actively
supported by the US, attacking not the own government but the United States might be an
auspicious option, in particular when the disliked home regime is stabilized by the US. Following
the assumption that the supporters of the hostile home government are considered as enemies, US
support may turn hate against local rulers into anti-US terrorism. In this paper we empirically
examine the effects of state repression and US closeness on anti-US terror in a panel of 149
2
countries for the period from 1981 to 2005. The results of the negative binomial regressions
indicate that abuses of the subset of human rights known as physical integrity rights as well as
dependence from the United States measured by economic and military aid are crucial factors
driving the extent of anti-US terrorism. In addition, we reveal that a combination of both
conditions increases the probability of anti-US terrorism over proportionately. The next section
reviews the relevant literature and theoretically motivates the formulation of the hypotheses to
test, section three illustrates the empirical design including the data and the methodology and
presents the results and section four concludes.
2 Theoretical Foundations and Related Literature
Rational theories assume terrorists and terrorist groups to follow an economic calculus (see, e.g.,
Sandler and Enders, 2004; Caplan, 2006; Anderton and Carter, 2005). Individual terrorist
behavior is regarded as a strategic weighing up of costs and benefits of achieving idealistic and
political goals (e.g. regime change, territorial change, political control). Terrorist attacks are seen
as a radical instrument to follow these goals by rebelling against the antagonistic home
government. Radical behavior is often seen as the only possibility to push political and
ideological values since first, the home country oftentimes does not allow peaceful political
participation – for example in autocratic countries – and second, the differences in power
between the home government and the radical group are too pronounced to permit a change in the
unaccepted status quo. Accordingly, for groups who are dissatisfied with the current economic
situation, and not in a position to bring drastic political and institutional changes, it can be
rational to engage in terrorism (Blomberg et al. 2004).
Considering the crucial determinants that trigger the participation in violent conflict, recent
literature has focused mainly on economic and political factors. In this vein Blomberg et al.
3
(2004), Freytag et al. (2011) and Gries and Meierrieks, (2013) suggest that poor economic
conditions promote terrorism and a wide body of literature focused on the nexus between
political institutions and terrorism analyzing if terrorism is more likely in non-democratic (e.g.,
Eyerman, 1998; Li, 2005, Piazza, 2008a) and politically unstable countries (e.g., KurrildKlitgaard et al., 2006; Hegre et al., 2001). However, coming from the assumption that terrorist
behavior is a reaction on the discontent relation with the government, we should give more
attention to government behavior and government effectiveness as potential drivers of terrorist
activity. Only few studies investigate the possible effect of governance and the government
manner in this context. Presumably, a malfunctioning political system and oppressive
government activity in terms of e.g. political violence and human rights violations may have a
strongly provoking effect on the emergence of oppositions against the government. In this
context Walsh and Piazza (2010) show that terrorist activity in a country is positively related to
local human rights violations. They suggest that states that violate the overall physical integrity
rights of their citizens are actually more frequently targeted by terrorists than those characterized
by a higher respect for such rights. This is also supported by Krueger and Maleckova (2003) and
Krueger and Laitin (2003) who find that repressive states are typical source countries of terror.
In search of an explanation for why the unaccepted status quo in the home country is also
projected on transnational targets – in particular the U.S. -, we follow a recent developed rational
theory of international terrorism, which argues that from a strategic perspective it makes sense for
terrorists to attack transnational goals, even if they ultimately intend to induce political change in
their home (Neumayer and Plümper, 2011). Often, repressive state behavior of the home
government is buttressed by foreign powers. In this case, the terrorists can have a strategic
interest in attacking nationals of these foreign countries. For instance, on the question why the
Taliban are fighting America in his “Letter to America”, Bin Laden gives the answer that “under
4
your supervision, consent and orders, the governments of our countries which act as your agents,
attack us on daily basis” (Bin Laden, 2002). So, it becomes clear, that though the goals are of
domestic nature, the discontent at home is not only directed against the home government but
also against alliances and supporters. Further, the higher the economic and political dependence
on the US, the more the dissatisfaction within the country is projected on the United States. In
summary, assuming that human rights violations and repressive governments might induce more
terrorism not only directed at the government but also politically close transnational targets, we
arrive at our first hypothesis to test:
Hypothesis 1a:
Anti-U.S. terrorists are more likely to come from countries with highly repressive
governments and violations of human rights.
Further, recent research provides insights that the extent of transnational terrorism is affected by
the quality of the relation of the home government and the target government. The domestic
political discontent is the stronger projected on America, the more the disliked home political
system is supported by the American government. According to the motto “the friend of my
enemy is my enemy”, Plümper and Neumayer (2010) argue that for terrorist groups which seek to
overthrow their home country’s political system it might be attractive to target foreign allies
which stabilize and support the home country. For the case of the US, Neumayer and Plümper
(2011) find that more anti-American terrorism emanates from countries that have a higher
military closeness measured by US military aid, arms transfers and stationed American military
personnel. In this context, aid flows should not be seen as unconditional gifts, but as political
strategies. For example Dreher et al. (2008) show that US aid flows go in line with voting
compliance of recipients in the UN General Assembly and Alessina and Dollar (2000) as well as
5
Sullivan et al. (2011) find evidence that foreign aid is determined by political and strategic
considerations and affects the foreign policy behavior. The aid flows, which are seen as support
of the local government, in turn might lead to increased transnational terrorism directed towards
the sending country. Considering the relationship between aid and terrorism, Boutton and Carter
(2013) demonstrate that anti US terrorism from a country is strongly correlated with US aid flows
entering that country and Bapat (2011) and Boutton (2013) show that US aid as counterterrorism
strategy is counterproductive and increases the extent of transnational terrorism against the US.
This leads us to our next hypothesis to test:
Hypothesis 1b:
Anti-U.S. terrorists are more likely to come from countries with a high military (military
aid) and economic (economic aid) dependence on the US.
Finally, based on the preposition of hypotheses 1a and 1b, we assume that the combination of
both terrorism driving factors, namely state repression and US support, might generate an overproportional effect on terrorism. The terrorism generating effects of aid flows might be higher in
countries with higher human rights violations, and the other way around, repression might boost
anti-US terrorism over proportionally in countries with high aid flows from the US. This leads to
the final hypothesis to test:
Hypothesis 2:
The effects of government repression and military and economic dependence on the US
interact, so that countries with both, high repression and high US dependence are even
more likely to be the origin of anti-US terrorism.
6
3 Empirical Design
In the analytical part of the paper an empirical design is established with the purpose of testing
the hypotheses developed in Chapter 2. The hypotheses are subjected to a formation of empirical
tests in the form of negative binomial statistical regression models using annual data from 149
countries over the period 1981-2005. In this section we describe the data – including the
dependent variable, the main explanatory constructs and the set of control variables – and
econometric methods. The summary statistics of all variables are reported in Table 1.
Table1: Summary statistics
Variable
Obs.
Mean
S.D.
Min
Max
US victims
2639
0.0966
0.9178
0
26
Us attacks
2639
0.3899
2.2489
0
88
Killings in anti US attacks
2639
0.4252
6.2839
0
263
Attacks with US victims
2639
0.3384
2.1772
0
90
Human rights violations
2560
3.1746
2.3098
0
8
Economic aid
2639
0.0029
0.0122
0
0.2875
Military aid
2639
0.0003
0.0016
0
0.0305
GDP p.c. (ln)
2639
8.6324
1.1628
5.0315
11.1971
GDP p.c. growth
2630
1.5897
6.9265
-64.3602
88.7483
Population (ln)
2639
9.3245
1.4510
5.7821
14.0779
Distance to the US (ln)
2639
8.3357
1.1698
0
9.0993
Regime stability
2639
27.5316
26.1525
1
136
State failure
2639
0.61709
1.6298
0
13.5
Trade openness
2639
72.5688
45.6322
1.0860
446.064
Government size
2639
17.6295
8.3704
3.05556
62.4492
7
3.1 Data
Dependent Variable: Anti-US terrorism
Since the intention is to test for possible sources of anti-American terrorism, we use bilateral
transnational terrorism data to compile anti-US terrorism – measured by US victims, US attacks,
killings in anti US attacks and attacks with US victims based on the International Terrorism:
Attributes of Terrorist Events (ITERATE) database.4 It contains data on the characteristics of
transnational terrorist groups, their activities with international impact, and the environment in
which they operate (Mickolus et al. 2007). We define transnational anti-US terrorism by incidents
carried out by basically autonomous non-state non-US actors on US citizens (irrespective of the
location of the incident), so that the country classification of the terrorism source is defined by
the nationality of the terrorist actor. The variable US victims is defined by the sum of US citizens
killed in terrorist attacks, the variable US attacks is defined by the number of attacks that
primarily victimized US citizens, the variable killings in anti US attacks quantifies the number of
killed people in these attacks, and the variable attacks with US victims is the number of all attacks
that victimized US citizens.
Independent Variables
Our key independent constructs to test the hypotheses developed in Chapter 2 involve the
repression of a terrorist’s home country government and the closeness of this government to the
US government. Further we assume a combined effect of both constructs captured by interaction
effects of both variables.
4
Terrorism is characterized as transnational when a terrorist incident in one country involves victims,
targets, institutions, governments, or citizens of another country.
8
Repression and Human Rights Violations
We measure the repressive behavior of a countries’ government using human rights violations
based on the physical integrity rights index from the Cingranelli and Richards (2010) (CIRI)
Human Rights data set. It is an additive measure consisting of four individual components:
(1) Torture – defined as the inhuman and degrading inflicting of extreme pain by purpose by
government officials or by private individuals at the instigation of government officials.
(2) Extrajudicial killings – defined as killings by government officials without due process of
law.
(3) Disappearances - characterized as cases in which people have disappeared, the victims have
not been found and political motivation appears likely.
(4) Political imprisonment – defined as the incarceration of people by government officials
because of: their speech; their non-violent opposition to government policies or leaders; their
religious attitudes; their non-violent religious practices including proselytizing; or their
associations in certain groups (ethnic, racial etc.).
Each of these sub-indices is built as ordinal scale with values ranging from 0 (practiced
frequently) over 1 (practiced occasionally) to 2 (did not occur), so the cumulative physical
integrity index ranges from 0 to 8. We rescale the variable, so that higher values go in line with
higher human rights violations and following Hypothesis 1a we expect a positive effect on antiUS terrorism.
9
Military and Economic Closeness
To measure the closeness of the home government to the US government we use military and
economic US support and dependence generated by military and economic aid from the US.
According to recent empirical studies investigating the relationship between aid flows and
political support of the receiving country, such as Alesina and Dolar (2000), Kuziemko and
Werker (2006), Dreher et al. (2008), Mesquita and Smith (2009) and Fleck and Kilby (2001,
2006) and Milner and Tingley (2010), assistance may not serve as an unselfish giveaway or
charity of donors, but as an investment with self-interest that may also be used to buy political
support from the recipients of aid. The data for economic and military aid flows is provided by
the USAID Economic Analysis and Data Services (EADS). This database offers information on
aid flows in constant dollars from the US to all receiving countries classified into assistance
programs since 1946.5 To control for scale effects we divide by national GDP.
Controls
To avoid the problem of spurious relationships between the dependent and the independent
variables, our baseline model controls for a number of variables commonly identified as potential
determinants of terrorism. In particular, we control for the impact of economic development,
population size, distance to the US, regime stability, and state failure.
5
We experimented also with alternative measures of military dependence like US military personal
measured as the ratio of US to domestic military personal stationed in the country and US arms exports
(divided by domestic military expenditures). The results support the general effect of military aid but are
not presented here due to space limitations (available upon request).
10
Economic Development
First, we account for the effect of economic development. Theoretically, the opportunity costs
reflected in a country’s economic development may influence the cost-benefit expectations of
terrorists and particularly their supporters (Freytag et al. 2011; Caplan, 2006, Sandler and Enders,
2004; Blomberg et al., 2004). The current empirical literature is highly suggestive that poor
economic development is a root cause of terrorism and increases the probability of terrorist attack
from that country (Blomberg et al., 2004; Freytag et al., 2011 and Gries and Meierrieks, 2013).
To control for the economic development of a country we use (logged) GDP per capita extracted
from the Penn World Table.
Population
Further, we account for the effect of population size on terrorism. From the theoretical
perspective countries with larger populations might have a larger potential for terrorism by
producing more potential groups and individuals willing to engage in terrorism. Further, more
populous countries might have higher monitoring costs making counter terrorism more difficult.
This perception is confirmed by numerous empirical studies which find that population size is
positively correlated with terrorism (e.g., Piazza, 2006; Li and Schaub, 2004; Burgoon, 2006).
The variable (logged) population size is also extracted from the Penn World Table.
Distance
Following the assumption that a higher distance between origin and target country is associated
with higher planning effort and higher costs for terrorist attacks we control for the distance using
the (logged) distance between Washington, D.C., and the respective foreign country’s capital as
reportet in the CEPII GEODist Database (Mayer and Zignago, 2011).
11
Regime stability
A broad field of literature has already investigated the influence of political institutions on the
extent of terrorism with mixed results. On the one hand, results of Piazza (2006), Eyerman
(1998), and Krueger and Laitin (2008) suggest that democracy can reduce terrorism. On the other
hand, studies of Li (2005), Blomberg and Hess (2008a, 2008b), Braithwaite and Li (2007) and
Burgoon (2006) present opposite results suggesting that liberal democracies are thought to
provide a favorable environment for terrorism by giving terrorists freedom of association and
movement. Abadie (2006) and Kurrild-Klitgaard et al. (2006) indicate a non-liner relationship
between political liberty and terrorism and suggest that democratic regimes as well as the
repressive practices commonly adopted by autocratic regimes may help keeping terrorism at bay.
They provide support that it is not primarily the regime type but regime stability has an effect on
the emergence of terrorism and that especially in times of regime changes and political transitions
political instabilities provide incentives and opportunities for terrorist groups to strike. We
control for regime stability using the regime durability variable from the Polity IV Project
operationalized by the number of years since the most recent regime change and expect a positive
effect on terrorism.
State failure
Finally, we control for state failure and assume it to have a positive effect on terrorism for the
same reasons as regime stability. Involving political instability, failed states might provide
conditions under which certain types of terrorist groups can operate. Results of Piazza (2007,
2008a, 2008b), Campos and Gassebner (2013) and Newman (2007) show that states that
experience more incidents of state failures are more likely to experience transnational terrorism.
We use the variable state failure from the State Failure Task Force database which measures the
12
intensity of revolutionary wars, ethnic wars, adverse regime changes, and genocides and
politicides.
While the former variables enter our baseline model, we run a battery of specifications including
further controls to assess the robustness of our findings. Specifically, to account for the auto
correlation structure of the dependent variable, we expand the specification by considering a lag
of the dependent variable as a regressor. Further, we analyze the influence of economic growth
(as an alternative to the level of development), the impact of trade openness and government
size.6
3.2 Econometric Methodology and Results
Since the set of our dependent variables is classified as count data variables, which assume only
discrete, non-negative values, a sporadic and rare nature of incidents with a high number of zeroobservations, an uneven distribution and a possible dependence between the incidents, we have to
apply a count-data regression technique accounting for the special structure of the data.
Furthermore, preliminary tests suggested overdispersion of the dependent variables;7 therefore we
estimate pooled negative-binomial regression models on our panel dataset.8
6
Further robustness checks control also for the effects of democracy, ethnic and religious tension and the
cold war period. The results are available upon request.
7
In the statistical sense overdispersion defines the situation when the variance of a variable is higher than
its mean.
8
Alternative estimation techniques like random effect negative-binomial regression and Poison regression
do not change the quality of our results To account for a possible problem of zero inflation we run also
zero inflated negative binomial regression as a robustness check which also support our main finding. The
results are available upon request.
13
3.2.1 Human Rights Violations and US Dependence
In a first step we test Hypotheses 1a and 1b and investigate the impact of human rights violations
and economic and military assistance on anti-US terrorism estimating a set of equations of the
following form:
terrorism i,t = α + β1 hr_violations i,t-1 + β2 aid i,t-1 + γ Z i,t-1 + ηi + µt + εi,t
where terrorism
i,t
(1)
is the dependent variable measured alternatively by US victims, US attacks,
killings in anti US attacks, or attacks with US victims in country i, hr_violations i,t-1 measures the
abuses in human rights quantified by the violations in physical integrity rights in country i and
aid i,t-1 represents alternatively the US economic or US military aid flows into country i. Z i,t-1 is a
set of control variables presented above, ηi and µt are region and time dummies and εi,t is the
disturbance term. To counteract the problem of a possible endogeneity between human rights
violations and terrorism and aid flows and terrorism and because we assume the independent
variable not to have an immediate but a deferred effect on the independent variable we let all
independent variables enter the model with a lag of one year. 9 The results are presented in Table
9
In the context of reverse causation Dreher et al. (2010) investigate the effect of counter terrorism on
human rights violations with the result that counter terrorism strategies, as an outcome of appearance of
terrorism have a negative impact on human rights. Piazza and Walsh (2009) investigate the effect of
terrorist attacks on human rights behavior of governments and find significant effects for a couple of
human rights categories. These results suggest a possibly endogenous relationship between terrorism and
human rights abuses in a country. Further, Azam and Thelen (2010) discuss a possible endogeneity
problem between aid and terrorism. To account for this possible endogeneity and to check the robustness
of the negative binomial regressions we additionally reverse the regression and account for a possible
effect of (lagged) terrorism on aid flows and (lagged) terrorism on human rights violations using the same
set of control variables. Our results indicate that a reverse causality is not present.
14
2, whereat the first four specifications present the results for economic aid and the last four for
military aid.10
We find a highly significant robust correlation between human rights violations and anti-US
terrorism from the respective country. Greater respect for physical integrity rights consistently
reduces anti-US terrorism regardless of the type of the dependent variable. This confirms
Hypothesis 1a and is in line with the prediction that anti-US terrorism is more likely to emerge in
countries with high repression measured by violations in physical integrity rights. This result is
similar to the findings of Walsh and Piazza (2010) who show that terrorist activity in a country is
positively related to local human rights violations. However, our results go even further and
suggest that government repression seems to provoke more terrorism not only directed on the
hostile government but also on politically close transnational targets. Political violence and
human rights violations seem to favor oppositions directed also towards countries supporting the
domestic power structure.
The coefficients of economic and military aid are positive and significant through all
specifications. This result confirms Hypothesis 1b and reveals that aid flows from the US increase
the probability of transnational US terrorism from that country so that anti-US terrorism is more
likely to have its genesis in countries with a high military and economic dependence on the US.
Our results confirm the findings of Neymayer and Plümper (2011) who show that attacking
foreign countries is the more attractive the more the home government depends on support from
the foreign country. In line with studies of Boutton and Carter (2013), Boutton (2013), Sullivan et
al. (2011), Findley (2012), and Young and Findley (2011) we show that aid flows, which are
10
Since economic and military aid are highly correlated we do not include both variables simultaneously
in one specification to avoid multicollinearity problems.
15
often addressed as instruments of counter terrorism strategies (Bandyopadhyay et al., 2011, Azam
and Delacroix, 2006) seem to have a counterproductive effect and rather drive terrorism directed
on US interests. As argued by Lizardo (2006) economic dependence and the influence of the US
seem to trigger fear of a cultural globalization and lead to an increase in anti-US terror.
Considering the set of control variables population size shows a consistently positive effect on
anti-US terrorism. It can be assumed that the pure size effect of the country and the associated
greater risk of the emergence of terrorism as well as higher monitoring costs are crucial. As
expected, state failure positively affects anti-US terror, indicating that countries with high
political instability may provide conditions under which terrorists and terrorist groups can
operate. This is also the case for regime stability, where the results show a negative effect of
regime durability on terror measured by US attacks and attacks with US victims. This is in line
with the studies of Abadie (2006) and Kurrild-Klitgaard et al. (2006) who argue that political
liberty has a non-linear effect on terrorism and not the regime type but the regime durability is
essential for poverty reduction.11 Finally, the distance to the US coefficient is positive albeit not
consistently significant. Surprisingly, this result is contrary to our assumption that transnational
terrorism decreases with increasing distance. However, one should bear in mind that the most
part of anti-US terrorism is not within America, so that the distance becomes less important.
To check the robustness of our main findings we implement a set of additional controls, namely
GDP per capita growth, trade openness and government size and include also a lag of the
dependent variable as a regressor. The results presented in Table 3 show that the identified
11
Alternatively to regime stability, we also account for the effect of democracy, however the results show
no significant effects.
16
positive effects of human rights violations and economic and military aid on anti-US terrorism
are robust and stay highly significant with the inclusion of alternative controls.
The positive effect of the lagged terrorism variable is in line with Freytag et al. (2011), Enders
and Sandler (2005) and Lai (2007) and suggests path dependence. For instance, longer terrorist
campaigns generate economies of scale by reducing per-incident costs and generating a higher
media attention. Considering the coefficients of economic growth, trade openness and
government size the results show no significant effects.
3.2.2 Interaction of Human Rights Violations and US Dependence
In a second step we test Hypothesis 2 and investigate the impact of a possible interaction effect of
human rights violations and military and economic dependence. We assume that the terrorism
generating effects of aid flows are bigger in countries with higher human rights violations, and
the other way around, that repression boosts anti-US terrorism over proportionally in countries
with high aid flows from the US. To account for this effect we augment model specification (1)
by the product of both predictors resulting in the following model:
terrorism i,t = α + β1 hr_violations i,t-1 + β2 aid i,t-1 + β3 (hr_violations* aid) i,t-1 + γ Z i,t-1 + ηi + µt + εi,t (2)
The interpretation of interaction terms in count models in not trivial. As shown in Ai and Norton
(2003) the magnitude of the interaction effect in nonlinear models does not equal the marginal
effect of the interaction term. A comprehensive analysis of interaction terms in negative binomial
models can be found in Hilbe (2011). Following this methodology we approach the analysis 1) by
binary interaction terms and 2) by continuous interaction terms.
17
Table 2: Human Rights Violations US Aid and anti US Terrorism – Baseline Regression
GDP p.c. (ln) t-1
Population (ln) t-1
HR violations t-1
Economic aid t-1
(1)
US victims
(2)
US attacks
1.035***
(0.290)
0.636***
(0.171)
0.391***
(0.096)
94.927***
(27.256)
0.494**
(0.209)
0.450***
(0.118)
0.319***
(0.064)
46.733**
(19.564)
(3)
Killings in
anti US
attacks
0.739**
(0.318)
0.857***
(0.203)
0.488***
(0.115)
135.987*
(71.749)
(4)
Attacks with
US victims
(5)
US victims
(6)
US attacks
0.380*
(0.208)
0.431***
(0.114)
0.339***
(0.069)
45.705**
(22.925)
0.963***
(0.307)
0.538***
(0.165)
0.410***
(0.095)
Military aid t-1
Distance (ln)
Regime stability t-1
State failure t-1
Mean VIF
Wald χ2
(Prob. > χ2)
LogPseudolikelihood
Observations
0.690
(0.428)
-0.003
(0.010)
0.274***
(0.085)
2.14
1455.81
0.00
-359.08
0.309***
(0.062)
-0.020***
(0.007)
0.141**
(0.067)
2.14
457.96
0.00
-1224.13
1.661*
(1.001)
-0.015
(0.011)
0.359*
(0.207)
2.14
725.53
0.00
-541.90
0.313***
(0.068)
-0.020***
(0.007)
0.167**
(0.067)
2.14
553.25
0.00
-1130.56
232.518***
(75.401)
0.575**
(0.258)
-0.005
(0.009)
0.264***
(0.080)
2.13
32724.10
0.00
-359.61
2420
2420
2420
2420
2420
(8)
Attacks with
US victims
0.428**
(0.208)
0.397***
(0.113)
0.312***
(0.060)
(7)
Killings in
anti US
attacks
0.673**
(0.315)
0.723***
(0.188)
0.529***
(0.110)
169.674***
(47.990)
0.290***
(0.060)
-0.020***
(0.007)
0.140**
(0.065)
2.13
444.73
0.00
-1219.51
325.097***
(120.394)
1.107
(0.752)
-0.015
(0.011)
0.317
(0.202)
2.13
783.77
0.00
-542.66
190.129***
(50.270)
0.294***
(0.072)
-0.021***
(0.006)
0.166**
(0.065)
2.13
601.74
0.00
-1122.39
2420
2420
2420
0.328
(0.212)
0.381***
(0.107)
0.335***
(0.065)
Notes: Constant not reported. All models include year and regional dummies (not reported). Robust standard errors clustered over countries in parentheses.
* p < 0.10, ** p < 0.05, *** p < 0
18
Table 3: Human Rights Violations US Aid and anti US Terrorism (US victim) – Additional Controls
US victims t-1
GDP p.c. (ln) t-1
(1)
US victims
0.359**
(0.156)
0.965***
(0.268)
GDP p.c. growth t-1
Population (ln) t-1
HR violations t-1
Economic aid t-1
0.600***
(0.163)
0.380***
(0.092)
89.102***
(25.543)
(2)
US victims
-0.036
(0.024)
0.500***
(0.169)
0.327***
(0.092)
58.223***
(20.380)
(3)
US victims
(4)
US victims
1.032***
(0.294)
1.107***
(0.299)
0.662***
(0.222)
0.397***
(0.110)
95.138***
(26.374)
0.658***
(0.183)
0.394***
(0.097)
95.191***
(26.673)
Military aid t-1
Distance (ln)
Regime stability t-1
State failure t-1
0.685
(0.437)
-0.004
(0.010)
0.273***
(0.083)
0.935
(0.735)
0.007
(0.011)
0.276***
(0.084)
Trade openness t-1
0.699
(0.425)
-0.004
(0.011)
0.272***
(0.087)
0.001
(0.011)
Government size t-1
Mean VIF
Wald χ2
(Prob. > χ2)
Log
Pseudolikelihood
Observations
0.670*
(0.387)
-0.005
(0.010)
0.263***
(0.092)
2.12
1659.99
0.00
-357.63
2.04
690.99
0.00
-364.78
2.16
3974.09
0.00
-359.05
0.012
(0.018)
2.17
1757.10
0.00
-358.92
2420
2420
2420
2420
(5)
US victims
0.420***
(0.142)
0.901***
(0.282)
(6)
US victims
0.505***
(0.153)
0.397***
(0.089)
-0.036
(0.024)
0.450***
(0.165)
0.340***
(0.091)
225.779***
(68.452)
0.566**
(0.263)
-0.005
(0.009)
0.261***
(0.078)
156.551**
(66.975)
0.727
(0.504)
0.006
(0.010)
0.270***
(0.080)
(7)
US victims
(8)
US victims
0.962***
(0.310)
1.017***
(0.330)
0.540**
(0.239)
0.410***
(0.103)
0.550***
(0.177)
0.413***
(0.095)
232.512***
(75.559)
0.575**
(0.258)
-0.005
(0.010)
0.263***
(0.082)
0.000
(0.011)
232.374***
(74.485)
0.569**
(0.250)
-0.005
(0.010)
0.256***
(0.088)
2.11
11769.01
0.00
-357.61
2.03
14448.14
0.00
-364.73
2.15
40118.74
0.00
-359.61
0.009
(0.019)
2.16
33010.88
0.00
-359.54
2420
2420
2420
2420
Notes: Constant not reported. All models include year and regional dummies (not reported). Robust standard errors clustered over countries in parentheses.
* p < 0.10, ** p < 0.05, *** p < 0
19
Binary interaction
Computing binary interactions allows us to account for different interaction coefficients and their
significance levels subjected to the value of the binary variables. The approach requires both
variables composing the interaction term to be binary. Therefore, we transform the variables
hr_violations and aid (economic and military) into dummy variables, where 1 denotes high
human rights violations and high aid flows and 0 respectively low values.12 Given that β1 is the
estimated coefficient for physical integrity rights, β2 is the estimated coefficient for economic or
military dependence and β3 is the estimated coefficient for their product, the risk ratios of the
interaction effects are calculated by:
exp[β1+ β3* aid] and
(3)
exp[β2+ β3* hr_violations].
(4)
Table 3 presents the results for all combinations of binary interaction including the coefficients,
the standard errors, and the incident rate ratios (IRR).13 The corresponding regression results are
presented in the Appendix in Table A1. 14
12
We construct the dummies according to the mean value of the variables, so that the dummy is 1 when
the value is higher than the mean and 0 when the value is lower than the mean. Alternatively, we also run
regressions with a dummy based on the median of the variables, however, our main findings do not
change.
13
The standard errors differ for each interaction combination. They are computed as the square root of the
variance of the interaction coefficient, which is V(β2)+ hr_violations2V(β3) + 2 * Cov (β2, β3) for equation
(3) and V(β2)+ aid2V(β3) + 2 * Cov (β2, β3) for equation (4).
14
We present only results for the dependent variable US victim. However, results for alternative dependent
variables like US attack, Killings in anti US incidents, and Incidents with US victims support our main
findings. Results are available upon request.
20
Table 4: Binary Interaction Effect of Human Rights Violations and Economic/Military Aid
Dummy relation
- high HR violations and high aid
: high HR violations and low aid
- high HR violations and low aid
: low HR violations and low aid
- high HR violations and high aid
: low HR violations and high aid
- low HR violations and high aid
: low HR violations and low aid
Economic Aid
Coef.
Std.
Err.
1.0472
0.6586
2.8497
Military Aid
Coef.
Std.
Err.
1.3385
0.6586
3.3677*** 1.1008
29.0117***
1.5838*
1.1008
4.8734*
1.7146*** 0.5768
5.5545***
1.160**
0.5768
3.1899**
4.0352*** 1.0824
56.5542***
1.4054*
1.0824
4.0772*
IRR
IRR
3.8133
Considering countries that receive high aid our results show that the incident rate ratios of high
human rights violations to low human rights violations are 5.5545 for economic aid and 3.1899
for military aid. These effects are significant and reveal that in countries with a high US
dependence terrorism is 555% and 319% more likely when human rights are violated. Further, in
countries with low human rights violations the emergence of anti US-terrorism is higher when the
aid flows from the US are high (5655% for economic and 408% for military aid) and focusing on
low aid countries we can identify a higher probability (2901% for economic and 487% for
military aid) for anti-US terrorism with predominant government repression. The results reveal
that the terrorism driving effects of repression and US dependence mutually depend on each
other. Anti US-terrorism is not only boosted by the isolated factors but rather by their
combination, here a repressive government structure plus a high economic and military
dependence on the US seem to create favoring conditions for its emergence.
Continuous interaction
In a next step we implement a continuous interaction term that provides more detailed
information on the impact of a variable in dependence on the value of the other variable. It allows
21
for a more precise analysis of the interdependencies of human rights violations and US
dependence on anti-US terrorism.
Adding an interaction computed as the product of two continuous variables to a model can result
in a host of coefficients. Assuming n values of human rights violations and m values of aid the
slope results in n * m separate coefficients. To present the results more clearly Hilbe (2011)
suggests to group continuous variables and to present the results for selected values. So we
compute the interaction coefficient holding one variable constant and varying the other whereat
we consider nine grades.15 The results for US victims as the dependent variable are presented in
Table 5 and 6, where Table 5 shows the effect of aid dependent on varying values of human
rights violations (according to equation (3)) and Table 6 shows the effect of human rights
violations for varying values of aid (according to equation (4)). The corresponding regression
results are presented in the Appendix in Table A2. The human rights violations value ranges
from 0 (no violations) to 8 (very high violations). The results reveal that the effect of economic
aid and military aid on US terrorism increases with increasing human rights violations. While for
countries with no human rights violations (HR violations =0) the IRR of economic aid is
6.53E+36, rising continuously with increasing repression arriving at a value of 1.74+E44 for the
highest repression (HR violations = 8). For military aid the IRR rises continuously from 1.13+E72
for very low repression to 9.29+E132 for high repression with the effect being significant for a
repression value of 2 upwards.
15
We group the ranges of the variables into nine categories. For human rights violations we consider all
integers from 0 to 8, which is exactly the range of the variable. For economic and military aid we consider
values ranging from the minimum to the maximum value of the variable, however in addition we weight
the intervals according to the distribution within the range.
22
Table 5: Effect of Economic Aid Dependent on the Value of HR Violations
HR
violations
value
0
1
2
3
4
5
6
7
8
Economic
aid
Coef.
84.78**
86.92***
89.06***
91.20***
93.33***
95.47***
97.61***
99.75***
101.89***
Std. Err
IRR
37.16
32.71
29.20
26.99
26.42
27.58
30.27
34.14
38.83
6.53E+36
5.55E+37
4.72+E38
3.97+E39
3.38+E40
2.87+E41
2.44+E42
2.07+E43
1.74+E44
HR
violations
value
0
1
2
3
4
5
6
7
8
Military
aid
Coef.
165.91
183.44
200.98*
218.51***
236.04***
253.58***
271.11**
288.64**
306.18*
Std. Err
IRR
170.93
136.05
104.44
80.08
70.87
82.08
107.51
139.59
174.69
1.13+E72
4.64+E79
1.93+E87
7.90+E94
3.24+E102
1.33+E110
5.52+E117
2.26+E125
9.29+E132
Considering the effect of human rights violations as a function of aid (Table 6) we can identify a
stronger effect with increasing aid flows. While for countries not receiving aid from the US a one
unit increase in human rights violation results in a 47% (economic aid) and 50% (military aid)
increase in US terrorism (given the other variables are held constant in the model). In countries
which are highly dependent on US aid flows a one unit increase in human rights violations results
in a 60% (economic aid) and 64% (military aid) increase in anti-US terrorism.
Table 6: Effect of Human Rights Violations Dependent on the Value of Economic Aid
Economic
aid
value
0
0.0001
0.0005
0.001
0.005
0.01
0.02
0.03
0.04
HR
violations
Coef.
0.3835***
0.3837***
0.3845***
0.3856***
0.3942***
0.4049***
0.4262***
0.4476**
0.4690*
Std. Err.
IRR
Military
aid value
0.1046
0.1043
0.1031
0.1017
0.0939
0.0950
0.1282
0.1821
0.2434
1.4673
1.4676
1.4689
1.4705
1.4845
1.4990
1.5384
1.5646
1.5982
0
0.000001
0.000005
0.00001
0.00005
0.0001
0.0005
0.001
0.005
HR
violations
Coef.
0.40402***
0.40404***
0.40411***
0.40420***
0.40490***
0.40578***
0.41279***
0.42156***
0.49169**
Std. Err.
IRR
0.0952
0.0952
0.0952
0.0952
0.0949
0.0946
0.0939
0.0966
0.2037
1.4978
1.4979
1.4980
1.4981
1.4981
1.5005
1.5110
1.5243
1.6351
23
So both, the results for the binary interaction as well as for the continuous interaction reveal that
the effects of home repression and US dependence should not be considered independently of
each other but, what is remarkable, that they influence each other.
In summary, we are able to confirm hypotheses 1a and 1b as well as hypothesis 2. Both,
repressive state behavior – measured by human rights violations – as well as a close relationship
of the home regime to the US – measured by economic and military aid flows from the US –
seem to increase anti US terrorism in each case. Further, interaction effects of these variables
show that a combination of state repression and state support by the US leads to an over
proportional effect. The discontent with the domestic regime is more strongly projected on the
US the more repression takes place in the country and the more the domestic political situation is
stabilized and supported by the US.
Conclusion
We investigate possible determinants of anti-US terrorism. In particular, we ask whether
oppressive governments and/or close connections with the US encourage attacks against the US.
We argue that oppressive state behavior, such as human rights violations, may provoke resistance
against the authorities, including violent attacks. Further, for terrorist groups which seek to
overthrow their home country’s political system it might be attractive to target the US as foreign
allies especially if the government’s capacity seems dependent on US support. Arriving at our
test hypotheses we assume that anti-U.S. terrorism is more likely to emerge in countries with
high repression (hypothesis 1a) and in countries with a high dependence to the US (hypothesis
1b). Further, a combination of both conditions may drive anti-US terrorism to an over
proportional degree (hypothesis 2). The negative binomial regressions for a panel of 149
countries from 1981 to 2005 indicate that both oppressiveness and US closeness are important
24
determinants of anti-US terrorism. In summary, we are able to confirm hypotheses 1a and 1b as
well as hypothesis 2. Both, repressive state behavior – measured by human rights violations – as
well as a close relationship of the home regime to the US – measured by economic and military
aid flows from the US – seem to increase anti-US terrorism in each case. Further, both effects do
not seem completely independent. Interaction effects of these variables show that a combination
of state repression and state support by the US leads to an over proportional effect. The
discontent with the domestic regime is more strongly projected on the US, the more repression
takes place in the country, and the more the domestic political situation is stabilized and
supported by the US.
25
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Appendix
Table A1: Human Rights Violations US Aid and anti US Terrorism (US victim) with Binary
Interaction
(1)
(2)
US victims
US victims
GDP p.c. (ln) t-1
1.018***
0.481*
(0.301)
(0.262)
Population (ln) t-1
0.358**
0.364**
(0.170)
(0.171)
Dummy (1) HR
3.368***
1.584*
violations t-1
(1.101)
(0.852)
Dummy (2.1)
4.035***
Economic aid t-1
(1.082)
Dummy (2.2)
1.405*
Military aid t-1
(0.725)
Interaction
-2.321**
(1)*(2.1)
(1.136)
Interaction
-0.245
(1)*(2.2)
(0.796)
Distance (ln)
1.159
0.608
(0.917)
(0.448)
Regime stability t-1
-0.011
-0.004
(0.009)
(0.009)
State failure t-1
0.522***
0.432***
(0.118)
(0.110)
Mean VIF
2.36
2.21
Wald χ2
5667.54
6769.22
(Prob. > χ2)
0.00
0.00
Log-404.24
-409.80
Pseudolikelihood
Observations
2513
2513
Robust standard errors clustered on countries in parentheses
* p < 0.10, ** p < 0.05, *** p < 0.01
32
Table A2: Human Rights Violations US Aid and anti US Terrorism (US victim) with Continuous
Interaction
(1)
(2)
US victims
US victims
GDP p.c. (ln) t-1
Population (ln) t-1
(1) HR violations t-1
(2.1) Economic aid t-1
1.030***
(0.289)
0.638***
(0.174)
0.383***
(0.105)
84.771**
(37.162)
(2.2) Military aid t-1
0.960***
(0.306)
0.538***
(0.164)
0.404***
(0.095)
165.911
(170.926)
Interaction
(1)*(2.1)
Interaction
(1)*(2.2)
2.138
(6.832)
Distance (ln)
0.694
(0.440)
-0.003
(0.010)
0.274***
(0.085)
-29.087***
(5.932)
2.16
1885.51
0.00
-359.06
17.533
(39.405)
0.579**
(0.264)
-0.005
(0.009)
0.260***
(0.079)
-26.558***
(5.176)
2.70
25414.75
0.00
-359.57
2420
2420
Regime stability t-1
State failure t-1
Constant
Mean VIF
Wald χ2
(Prob. > χ2)
LogPseudolikelihood
Observations
Robust standard errors clustered on countries in parentheses
* p < 0.10, ** p < 0.05, *** p < 0.01
33