Journal of the Royal Statistical Society: Series C (Applied Statistics)
We develop a new statistical model to analyse time-varying ranking data. The model can be used wi... more We develop a new statistical model to analyse time-varying ranking data. The model can be used with a large number of ranked items, accommodates exogenous time-varying covariates and partial rankings, and is estimated via maximum likelihood in a straightforward manner. Rankings are modelled using the Plackett-Luce distribution with time-varying worth parameters that follow a mean-reverting time series process. To capture the dependence of the worth parameters on past rankings, we utilize the conditional score in the fashion of the generalized autoregressive score (GAS) models. Simulation experiments show that small-sample properties of the maximum-likelihood estimator improve rapidly with the length of the time series and suggest that statistical inference relying on conventional Hessian-based standard errors is usable even for medium-sized samples. As an illustration, we apply the model to the results of the Ice Hockey World Championships. We also discuss applications to rankings based on underlying indices, repeated surveys, and non-parametric efficiency analysis.
Fast food chains have long been setting an example in operations management e ciency; however, as... more Fast food chains have long been setting an example in operations management e ciency; however, as we show in the paper, there is still room for improvement. Our case study deals with crew optimization in a particular fast food restaurant. First, we describe the current practice in crew scheduling which is mostly done manually by the employees. Next, we provide two alternative MILP formulations that can be used to nd the optimal schedule under the given criteria; these formulations take into account the speci c crew structure of the fast food restaurant (full-time vs. part-time employees, underage temporary jobs etc.), as well as its speci c criteria. We discuss and compare the computational tractability of the proposed models for small-scale applications and comment on solution concepts for large-scale ones. Finally, we evaluate the restaurant's crew scheduling e ciency by comparing the quality of the actual (empiric) schedules to those obtained by MILP.
Despite recent emergence of studies inspired by Panel Study on Entrepreneurial Dynamics, the theo... more Despite recent emergence of studies inspired by Panel Study on Entrepreneurial Dynamics, the theory of new business foundation is far from developed. The aim of the paper is to analyze factors influencing birth and survival of early-stage entrepreneurial activity in the Czech Republic. Compared to previous Czech studies, this paper stands out in two directions. Firstly, it is based on a more robust and representative sample than previous studies. We use data on 371early-stage entrepreneurs that come from two longitudinal studies conducted between 2011 and 2014 in the frame of the Global Entrepreneurship Monitor project. Secondly, it puts a special focus on entrepreneurs who are already running their start-ups. We employ logistic regression to analyze differences in the effects of factors influencing these entrepreneurs and the ones who have only reached the nascent phase. The paper provides added value for our understanding of early-stage entrepreneurial dynamics.
Human populations tend to grow steadily, because of the ability of people to make innovations, an... more Human populations tend to grow steadily, because of the ability of people to make innovations, and thus overcome and extend the limits imposed by natural resources. It is therefore questionable whether traditional concepts of population ecology, including environmental carrying capacity, can be applied to human societies. The existence of carrying capacity cannot be simply inferred from population time-series, but it can be indicated by the tendency of populations to return to a previous state after a disturbance. So far only indirect evidence at a coarse-grained scale has indicated the historical existence of human carrying capacity. We analysed unique historical population data on 88 settlements before and after the Thirty Years War (1618-1648), one the longest and most destructive conflicts in European history, which reduced the population of Central Europe by 30-50%. The recovery rate of individual settlements after the war was positively correlated with the extent of the distur...
Recent studies showed that climate changes shape species distribution and could cause range shift... more Recent studies showed that climate changes shape species distribution and could cause range shifts in the flyway level of the species. Here, we demonstrated changes in species habitat selection as a response to weather severity in twelve most abundant wintering waterbird species with prevailing increase in numbers during three investigated periods (1972-1978, 1987-1993 and 2003-2009). We used wintering waterbird counts from 93 sites throughout the Czech Republic from mid-January term as the coldest period of winter when the effect of thermoregulation on wintering waterbirds distribution is most apparent. We recorded no significant changes in weather severity in three investigated periods in our study area, and hence we considered the effect of preference of cold weather refuge sites, i.e. habitats which can reduce negative effect of cold weather (running waters, urban area and extensive water surface area). We found prevailing effect of weather severity in the first period what may show thermoregulatory effects being expressed by weather severity on species habitat selection in the next period in six of the twelve investigated species (Mute Swan Cygnus olor, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, Little Grebe Tachybaptus ruficollis, Common Moorhen Gallinula chloropus and Common Coot Fulica atra). In the face of recent climate change and in spite of the increasing importance of wetlands in the Czech Republic for wintering waterbirds, the suitability of these sites for wintering is likely temperature-dependent. Thus, the preference of cold weather refuges reducing the effect of winter harshness becomes important in individual species.
A high proportion of nascent entrepreneurs do not make it to an operational venture. Eventhough e... more A high proportion of nascent entrepreneurs do not make it to an operational venture. Eventhough entrepreneurial exit decisions occur more frequently than many think, the literature on entrepreneurial discontinuance is not much developed. The paper first examines whether factors influencing early-stage discontinuance differ in the Czech Republic in comparison with Western countries. Second, it contributes to existing theories on nascent entrepreneurial activity of "modest majority" low-growth businesses by focusing on the role of expectations in discontinuance decisions. A sample of nascent entrepreneurs was interviewed in 2011 and then in two follow-up waves in 2012 and 2013. Building on hubris theory of entrepreneurship and theory of performance thresholds, the paper discusses subjective decision-making about entrepreneurial launch and exit. The results show that people with higher industry experience are more likely to discontinue from nascent entrepreneurship, a finding...
Central European Journal of Operations Research, 2015
The paper addresses the issue of online advertising efficiency in the context of the "banner blin... more The paper addresses the issue of online advertising efficiency in the context of the "banner blindness" phenomenon. We extend the traditional exposure metric of banner efficiency by allowing the effect of a banner display (exposure effect, EE) to vary depending on the sequence of pages that lead to the display. Within a user session on the given website, we assume that EE differs for a banner carried over from the previous page (low EE), from the case where the banner suddenly appears in a previously unoccupied place (high EE). This assumption implies that a banner's efficiency can be increased by optimising its placement throughout the website's structure; to this end, we develop a simple model framework. First, we formalize the efficiency metric based on expected total EE for a representative user, using a Markov chain model estimable from the website's clickstream data. Next, we formulate the selection of efficient banner placement as a mixed integer linear programming problem. We consider two scenarios: (i) a static one, where banner placement is fixed throughout the day, and (ii) a dynamic one, where banner placement is allowed to vary in different time intervals in order to respond to changes in browsing patterns. Finally, we demonstrate the use of our model on an empiric case study, and analyse the effect of different parameter settings.
Shrews have rich vocal repertoires that include vocalizations within the human audible frequency ... more Shrews have rich vocal repertoires that include vocalizations within the human audible frequency range and ultrasonic vocalizations. Here, we recorded and analyzed in detail the acoustic structure of a vocalization with unclear functional significance that was spontaneously produced by 15 adult, captive Asian house shrews (Suncus murinus) while they were lying motionless and resting in their nests. This vocalization was usually emitted repeatedly in a long series with regular intervals. It showed some structural variability; however, the shrews most frequently emitted a tonal, low-frequency vocalization with minimal frequency modulation and a low, non-vocal click that was clearly noticeable at its beginning. There was no effect of sex, but the acoustic structure of the analyzed vocalizations differed significantly between individual shrews. The encoded individuality was low, but it cannot be excluded that this individuality would allow discrimination of family members, i.e., a male and female with their young, collectively resting in a common nest. The question remains whether the Asian house shrews indeed perceive the presence of their mates, parents or young resting in a common nest via the resting-associated vocalization and whether they use it to discriminate among their family members. Additional studies are needed to explain the possible functional significance of resting-associated vocalizations emitted by captive Asian house shrews. Our study highlights that the acoustic communication of shrews is a relatively understudied topic, particularly considering that they are highly vocal mammals.
Nest survival in fragmented wetlands is usually affected by micro-habitat variables. The main aim... more Nest survival in fragmented wetlands is usually affected by micro-habitat variables. The main aim of the study was to investigate the factors affecting Reed Bunting Emberiza schoeniclus nest survival in wetland habitats within a mosaic Central European land-scape. In total, we monitored 95 nests on five separate fishponds in South Bohemia, Czech Republic during a six-year study between 2002 and 2007. In order to determine the effects on nest survival of nest site characteristic, the first egg laying date and nest age, we estimated daily survival rate (DSR) and built models using program MARK. DSR was significantly higher in nests located in Reed Canary Grass Phalaris arundinacea and tall vegetation Cattail Typha latifolia and Common Reed Phragmites australis than in sedges Carex spp. Surprisingly, expanding Reed Canary Grass was occupied later in the breeding season and likely less preferred vegetation type than sedges. Structure of sedge tussocks changed due to eutrophication and l...
In various research fields, from archaeology to landscape history and ecology, it is important to... more In various research fields, from archaeology to landscape history and ecology, it is important to know the date of the origin of historical settlements (i.e. towns, villages, hamlets, isolated farms) as precisely as possible. In Central Europe, there are two primary ways to obtain the date when a settlement was founded: “historical dating” (based on historical written sources) and “archaeological dating” (based on archaeological findings). Historical dating usually does not reflect the real time of origin, since the first reference to a settlement in written sources can be recorded many years after the real origin of the settlement. However, the time lag is unknown. Until now, no study has attempted to show exactly how the time lag differs in different centuries, or whether the time lag has been affected by any geographical factors. This paper compares the dates of origin from archaeological data and from written sources of medieval and early modern settlements (n ¼ 527, AD 850–1600) in the present-day Czech Republic. We also tested the influence of local environmental conditions on the time lag. Our comparison shows that the time lag has been decreasing with the passing of calendar years (from a time lag of 250 years for AD 1000 to approx. 80 years for AD 1400). Towns and places close to major towns also have a shorter time lag in their historical dating (the difference is almost 100 years). These results make an interpretation of the historical dating of medieval towns and villages more complicated. The length of the time lag and its dispersion means that, for the purposes of settlement dating, historical dating needs to be combined with other dating methods (especially in the medieval period). Our results also identify a possible bias in the chronology of landscape transformation.
Journal of International Migration and Integration, 2016
International migration influences economies of both the home and the host country. Some countrie... more International migration influences economies of both the home and the host country. Some countries perceive immigration as a threat and consider limitations to their social security system to protect the domestic economy. Within the European Union, both the economic and the legal side of the issue must be taken into account. The paper presents an empirical analysis of natives’ and immigrants’ unemployment rates in EU15 countries and discusses a possible use of the findings in intra-EU migration policy. Using Labour Force Survey Data for 2012, we estimate a series of logistic regressions in order to compare the immigrant/native unemployment rates, considering the differences in the structure of both subpopulations (in terms of age, sex, education and types of jobs). We conclude that a substantial part of the gap between natives’ and immigrants’ unemployment rates can be explained by these additional characteristics in most of the EU15 countries.
This paper helps to understand why some nascent entrepreneurs are successful in getting their new... more This paper helps to understand why some nascent entrepreneurs are successful in getting their new business operational while others are not and terminate their effort. We interviewed eighty one nascent entrepreneurs in the Czech Republic in 2011 and then again in 2012. The results of binary and multinomial logistic regressions show that nascent entrepreneurs who spent less time on developing their business, stayed longer in the "just trying" status and feared of failure were less likely to get their business operational within the next year. Previous industry experience and competition mapping lowered the probability of getting operational as well. On the other hand, entrepreneurial self-efficacy led to positive outcomes of venture creation effort. Finally, the study dealt also with growth expectations and found out that moderate expectations were increasing the probability of an actual launch. Abstrakt Tento článek pomáhá porozumět tomu, proč se některým jedincům zapojeným do rané podnikatelské aktivity podaří zprovoznit novou firmu, zatímco jiným nikoli, a svou aktivitu skončí. Užitou metodologií je binární a multinomiální regresní analýza souboru primárních dat o jedenaosmdesáti rodících se podnikatelích získaných na základě longitudinálního šetření provedeného v České republice v letech 2011 a 2012. Ukazuje se, že rodící se podnikatelé, kteří rozvoji svého podnikání věnovali méně času, setrvávali déle ve stavu před založením nebo se báli neúspěchu, zprovoznili své podnikání během následujícího roku s menší pravděpodobností. Stejně tak snižovaly pravděpodobnost zprovoznění předchozí oborové zkušenosti a zmapování konkurence. Podnikatelská sebedůvěra naopak ovlivnila výsledek úsilí o založení firmy pozitivně. Studie se rovněž zabývala růstovými očekáváními a došla k závěru, že středně velká očekávání zvyšují pravděpodobnost skutečného zprovoznění. 1 This study was supported by the University of Economics, Prague; project Explaining the causes of success and failure in the process of venturing and early growth of new firms in the Czech Republic (IP303032).
ABSTRACT Many mathematical models in economics can be described using either matrices or graphs. ... more ABSTRACT Many mathematical models in economics can be described using either matrices or graphs. First, we argue that the graphical approach deserves more attention than it typically gets at the Czech university courses; we suggest that students should be (i) encouraged to develop and use formal graphical models and (ii) taught how to translate between graphical and matrix results, so that they could freely choose the modelling framework that suits them best in a particular application. Second, we present a particular connection between graphs and matrices that we have found to be quite useful in several types of models. Finally, we show three different applications of this connection - in structural analysis, Markov chains, and structural equation modelling - and we comment on our classroom experience with their use.
In a centralized (or integrated) supply chain (CSC) the prices within the supply chain are set so... more In a centralized (or integrated) supply chain (CSC) the prices within the supply chain are set so as to maximize the total profit of the whole chain. In a decentralized supply chain (DSC) each agent sets the price of his/her production so as to maximize his/her own profit; as each agent's profit is influenced by the prices set by the remaining agents, the optimal pricing strategy for all the agents has to be the Nash-equilibrium one. The resulting profit of the DSC is always lower than the profit of its centralized counterpart due to the effect of double marginalization, and the efficiency of the DSC can be expressed as the ratio of the two profits. This paper analyzes the efficiency of non-cooperative decentralized supply chains with different types of supply chain architecture (serial, parallel, and combined) via a stylized model in deterministic environment. The Nash-equilibrium pricing strategies of the individual agents are derived for every type of architecture, and the resulting profits are compared. Furthermore, the way the total profit of a SC is split over the individual agents is discussed; it's demonstrated how a change in an individual agent's production cost affects not only the individual profit of the agent in question, but also (through positive externalities) the profit of all agents along the supply chain.
Journal of the Royal Statistical Society: Series C (Applied Statistics)
We develop a new statistical model to analyse time-varying ranking data. The model can be used wi... more We develop a new statistical model to analyse time-varying ranking data. The model can be used with a large number of ranked items, accommodates exogenous time-varying covariates and partial rankings, and is estimated via maximum likelihood in a straightforward manner. Rankings are modelled using the Plackett-Luce distribution with time-varying worth parameters that follow a mean-reverting time series process. To capture the dependence of the worth parameters on past rankings, we utilize the conditional score in the fashion of the generalized autoregressive score (GAS) models. Simulation experiments show that small-sample properties of the maximum-likelihood estimator improve rapidly with the length of the time series and suggest that statistical inference relying on conventional Hessian-based standard errors is usable even for medium-sized samples. As an illustration, we apply the model to the results of the Ice Hockey World Championships. We also discuss applications to rankings based on underlying indices, repeated surveys, and non-parametric efficiency analysis.
Fast food chains have long been setting an example in operations management e ciency; however, as... more Fast food chains have long been setting an example in operations management e ciency; however, as we show in the paper, there is still room for improvement. Our case study deals with crew optimization in a particular fast food restaurant. First, we describe the current practice in crew scheduling which is mostly done manually by the employees. Next, we provide two alternative MILP formulations that can be used to nd the optimal schedule under the given criteria; these formulations take into account the speci c crew structure of the fast food restaurant (full-time vs. part-time employees, underage temporary jobs etc.), as well as its speci c criteria. We discuss and compare the computational tractability of the proposed models for small-scale applications and comment on solution concepts for large-scale ones. Finally, we evaluate the restaurant's crew scheduling e ciency by comparing the quality of the actual (empiric) schedules to those obtained by MILP.
Despite recent emergence of studies inspired by Panel Study on Entrepreneurial Dynamics, the theo... more Despite recent emergence of studies inspired by Panel Study on Entrepreneurial Dynamics, the theory of new business foundation is far from developed. The aim of the paper is to analyze factors influencing birth and survival of early-stage entrepreneurial activity in the Czech Republic. Compared to previous Czech studies, this paper stands out in two directions. Firstly, it is based on a more robust and representative sample than previous studies. We use data on 371early-stage entrepreneurs that come from two longitudinal studies conducted between 2011 and 2014 in the frame of the Global Entrepreneurship Monitor project. Secondly, it puts a special focus on entrepreneurs who are already running their start-ups. We employ logistic regression to analyze differences in the effects of factors influencing these entrepreneurs and the ones who have only reached the nascent phase. The paper provides added value for our understanding of early-stage entrepreneurial dynamics.
Human populations tend to grow steadily, because of the ability of people to make innovations, an... more Human populations tend to grow steadily, because of the ability of people to make innovations, and thus overcome and extend the limits imposed by natural resources. It is therefore questionable whether traditional concepts of population ecology, including environmental carrying capacity, can be applied to human societies. The existence of carrying capacity cannot be simply inferred from population time-series, but it can be indicated by the tendency of populations to return to a previous state after a disturbance. So far only indirect evidence at a coarse-grained scale has indicated the historical existence of human carrying capacity. We analysed unique historical population data on 88 settlements before and after the Thirty Years War (1618-1648), one the longest and most destructive conflicts in European history, which reduced the population of Central Europe by 30-50%. The recovery rate of individual settlements after the war was positively correlated with the extent of the distur...
Recent studies showed that climate changes shape species distribution and could cause range shift... more Recent studies showed that climate changes shape species distribution and could cause range shifts in the flyway level of the species. Here, we demonstrated changes in species habitat selection as a response to weather severity in twelve most abundant wintering waterbird species with prevailing increase in numbers during three investigated periods (1972-1978, 1987-1993 and 2003-2009). We used wintering waterbird counts from 93 sites throughout the Czech Republic from mid-January term as the coldest period of winter when the effect of thermoregulation on wintering waterbirds distribution is most apparent. We recorded no significant changes in weather severity in three investigated periods in our study area, and hence we considered the effect of preference of cold weather refuge sites, i.e. habitats which can reduce negative effect of cold weather (running waters, urban area and extensive water surface area). We found prevailing effect of weather severity in the first period what may show thermoregulatory effects being expressed by weather severity on species habitat selection in the next period in six of the twelve investigated species (Mute Swan Cygnus olor, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, Little Grebe Tachybaptus ruficollis, Common Moorhen Gallinula chloropus and Common Coot Fulica atra). In the face of recent climate change and in spite of the increasing importance of wetlands in the Czech Republic for wintering waterbirds, the suitability of these sites for wintering is likely temperature-dependent. Thus, the preference of cold weather refuges reducing the effect of winter harshness becomes important in individual species.
A high proportion of nascent entrepreneurs do not make it to an operational venture. Eventhough e... more A high proportion of nascent entrepreneurs do not make it to an operational venture. Eventhough entrepreneurial exit decisions occur more frequently than many think, the literature on entrepreneurial discontinuance is not much developed. The paper first examines whether factors influencing early-stage discontinuance differ in the Czech Republic in comparison with Western countries. Second, it contributes to existing theories on nascent entrepreneurial activity of "modest majority" low-growth businesses by focusing on the role of expectations in discontinuance decisions. A sample of nascent entrepreneurs was interviewed in 2011 and then in two follow-up waves in 2012 and 2013. Building on hubris theory of entrepreneurship and theory of performance thresholds, the paper discusses subjective decision-making about entrepreneurial launch and exit. The results show that people with higher industry experience are more likely to discontinue from nascent entrepreneurship, a finding...
Central European Journal of Operations Research, 2015
The paper addresses the issue of online advertising efficiency in the context of the "banner blin... more The paper addresses the issue of online advertising efficiency in the context of the "banner blindness" phenomenon. We extend the traditional exposure metric of banner efficiency by allowing the effect of a banner display (exposure effect, EE) to vary depending on the sequence of pages that lead to the display. Within a user session on the given website, we assume that EE differs for a banner carried over from the previous page (low EE), from the case where the banner suddenly appears in a previously unoccupied place (high EE). This assumption implies that a banner's efficiency can be increased by optimising its placement throughout the website's structure; to this end, we develop a simple model framework. First, we formalize the efficiency metric based on expected total EE for a representative user, using a Markov chain model estimable from the website's clickstream data. Next, we formulate the selection of efficient banner placement as a mixed integer linear programming problem. We consider two scenarios: (i) a static one, where banner placement is fixed throughout the day, and (ii) a dynamic one, where banner placement is allowed to vary in different time intervals in order to respond to changes in browsing patterns. Finally, we demonstrate the use of our model on an empiric case study, and analyse the effect of different parameter settings.
Shrews have rich vocal repertoires that include vocalizations within the human audible frequency ... more Shrews have rich vocal repertoires that include vocalizations within the human audible frequency range and ultrasonic vocalizations. Here, we recorded and analyzed in detail the acoustic structure of a vocalization with unclear functional significance that was spontaneously produced by 15 adult, captive Asian house shrews (Suncus murinus) while they were lying motionless and resting in their nests. This vocalization was usually emitted repeatedly in a long series with regular intervals. It showed some structural variability; however, the shrews most frequently emitted a tonal, low-frequency vocalization with minimal frequency modulation and a low, non-vocal click that was clearly noticeable at its beginning. There was no effect of sex, but the acoustic structure of the analyzed vocalizations differed significantly between individual shrews. The encoded individuality was low, but it cannot be excluded that this individuality would allow discrimination of family members, i.e., a male and female with their young, collectively resting in a common nest. The question remains whether the Asian house shrews indeed perceive the presence of their mates, parents or young resting in a common nest via the resting-associated vocalization and whether they use it to discriminate among their family members. Additional studies are needed to explain the possible functional significance of resting-associated vocalizations emitted by captive Asian house shrews. Our study highlights that the acoustic communication of shrews is a relatively understudied topic, particularly considering that they are highly vocal mammals.
Nest survival in fragmented wetlands is usually affected by micro-habitat variables. The main aim... more Nest survival in fragmented wetlands is usually affected by micro-habitat variables. The main aim of the study was to investigate the factors affecting Reed Bunting Emberiza schoeniclus nest survival in wetland habitats within a mosaic Central European land-scape. In total, we monitored 95 nests on five separate fishponds in South Bohemia, Czech Republic during a six-year study between 2002 and 2007. In order to determine the effects on nest survival of nest site characteristic, the first egg laying date and nest age, we estimated daily survival rate (DSR) and built models using program MARK. DSR was significantly higher in nests located in Reed Canary Grass Phalaris arundinacea and tall vegetation Cattail Typha latifolia and Common Reed Phragmites australis than in sedges Carex spp. Surprisingly, expanding Reed Canary Grass was occupied later in the breeding season and likely less preferred vegetation type than sedges. Structure of sedge tussocks changed due to eutrophication and l...
In various research fields, from archaeology to landscape history and ecology, it is important to... more In various research fields, from archaeology to landscape history and ecology, it is important to know the date of the origin of historical settlements (i.e. towns, villages, hamlets, isolated farms) as precisely as possible. In Central Europe, there are two primary ways to obtain the date when a settlement was founded: “historical dating” (based on historical written sources) and “archaeological dating” (based on archaeological findings). Historical dating usually does not reflect the real time of origin, since the first reference to a settlement in written sources can be recorded many years after the real origin of the settlement. However, the time lag is unknown. Until now, no study has attempted to show exactly how the time lag differs in different centuries, or whether the time lag has been affected by any geographical factors. This paper compares the dates of origin from archaeological data and from written sources of medieval and early modern settlements (n ¼ 527, AD 850–1600) in the present-day Czech Republic. We also tested the influence of local environmental conditions on the time lag. Our comparison shows that the time lag has been decreasing with the passing of calendar years (from a time lag of 250 years for AD 1000 to approx. 80 years for AD 1400). Towns and places close to major towns also have a shorter time lag in their historical dating (the difference is almost 100 years). These results make an interpretation of the historical dating of medieval towns and villages more complicated. The length of the time lag and its dispersion means that, for the purposes of settlement dating, historical dating needs to be combined with other dating methods (especially in the medieval period). Our results also identify a possible bias in the chronology of landscape transformation.
Journal of International Migration and Integration, 2016
International migration influences economies of both the home and the host country. Some countrie... more International migration influences economies of both the home and the host country. Some countries perceive immigration as a threat and consider limitations to their social security system to protect the domestic economy. Within the European Union, both the economic and the legal side of the issue must be taken into account. The paper presents an empirical analysis of natives’ and immigrants’ unemployment rates in EU15 countries and discusses a possible use of the findings in intra-EU migration policy. Using Labour Force Survey Data for 2012, we estimate a series of logistic regressions in order to compare the immigrant/native unemployment rates, considering the differences in the structure of both subpopulations (in terms of age, sex, education and types of jobs). We conclude that a substantial part of the gap between natives’ and immigrants’ unemployment rates can be explained by these additional characteristics in most of the EU15 countries.
This paper helps to understand why some nascent entrepreneurs are successful in getting their new... more This paper helps to understand why some nascent entrepreneurs are successful in getting their new business operational while others are not and terminate their effort. We interviewed eighty one nascent entrepreneurs in the Czech Republic in 2011 and then again in 2012. The results of binary and multinomial logistic regressions show that nascent entrepreneurs who spent less time on developing their business, stayed longer in the "just trying" status and feared of failure were less likely to get their business operational within the next year. Previous industry experience and competition mapping lowered the probability of getting operational as well. On the other hand, entrepreneurial self-efficacy led to positive outcomes of venture creation effort. Finally, the study dealt also with growth expectations and found out that moderate expectations were increasing the probability of an actual launch. Abstrakt Tento článek pomáhá porozumět tomu, proč se některým jedincům zapojeným do rané podnikatelské aktivity podaří zprovoznit novou firmu, zatímco jiným nikoli, a svou aktivitu skončí. Užitou metodologií je binární a multinomiální regresní analýza souboru primárních dat o jedenaosmdesáti rodících se podnikatelích získaných na základě longitudinálního šetření provedeného v České republice v letech 2011 a 2012. Ukazuje se, že rodící se podnikatelé, kteří rozvoji svého podnikání věnovali méně času, setrvávali déle ve stavu před založením nebo se báli neúspěchu, zprovoznili své podnikání během následujícího roku s menší pravděpodobností. Stejně tak snižovaly pravděpodobnost zprovoznění předchozí oborové zkušenosti a zmapování konkurence. Podnikatelská sebedůvěra naopak ovlivnila výsledek úsilí o založení firmy pozitivně. Studie se rovněž zabývala růstovými očekáváními a došla k závěru, že středně velká očekávání zvyšují pravděpodobnost skutečného zprovoznění. 1 This study was supported by the University of Economics, Prague; project Explaining the causes of success and failure in the process of venturing and early growth of new firms in the Czech Republic (IP303032).
ABSTRACT Many mathematical models in economics can be described using either matrices or graphs. ... more ABSTRACT Many mathematical models in economics can be described using either matrices or graphs. First, we argue that the graphical approach deserves more attention than it typically gets at the Czech university courses; we suggest that students should be (i) encouraged to develop and use formal graphical models and (ii) taught how to translate between graphical and matrix results, so that they could freely choose the modelling framework that suits them best in a particular application. Second, we present a particular connection between graphs and matrices that we have found to be quite useful in several types of models. Finally, we show three different applications of this connection - in structural analysis, Markov chains, and structural equation modelling - and we comment on our classroom experience with their use.
In a centralized (or integrated) supply chain (CSC) the prices within the supply chain are set so... more In a centralized (or integrated) supply chain (CSC) the prices within the supply chain are set so as to maximize the total profit of the whole chain. In a decentralized supply chain (DSC) each agent sets the price of his/her production so as to maximize his/her own profit; as each agent's profit is influenced by the prices set by the remaining agents, the optimal pricing strategy for all the agents has to be the Nash-equilibrium one. The resulting profit of the DSC is always lower than the profit of its centralized counterpart due to the effect of double marginalization, and the efficiency of the DSC can be expressed as the ratio of the two profits. This paper analyzes the efficiency of non-cooperative decentralized supply chains with different types of supply chain architecture (serial, parallel, and combined) via a stylized model in deterministic environment. The Nash-equilibrium pricing strategies of the individual agents are derived for every type of architecture, and the resulting profits are compared. Furthermore, the way the total profit of a SC is split over the individual agents is discussed; it's demonstrated how a change in an individual agent's production cost affects not only the individual profit of the agent in question, but also (through positive externalities) the profit of all agents along the supply chain.
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Papers by Jan Zouhar