scholarly journals Drivers of diversity in individual life courses: Sensitivity of the population entropy of a Markov chain

2017 ◽  
Author(s):  
Ulrich K. Steiner ◽  
Shripad Tuljapurkar
Keyword(s):  
Markov Chain ◽  
Population Growth ◽  
Evolutionary Dynamics ◽  
Early Stage ◽  
Structured Populations ◽  
Individual Life ◽  
Individual Level ◽  
Selective Forces ◽  
Life Courses ◽  
Population Entropy

AbstractIndividuals differ in their life courses, but how this diversity is generated, how it has evolved and how maintained is less understood. However, this understanding is crucial to comprehend evolutionary and ecological population dynamics. In structured populations, individual life courses represent sequences of stages that end in death. These sequences can be described by a Markov chain and individuals diversify over the course of their lives by transitioning through diverse discrete stages. The rate at which stage sequences diversify with age can be quantified by the population entropy of a Markov chain. Here, we derive sensitivities of the population entropy of a Markov chain to identify which stage transitions generate—or contribute—most to diversification in stage sequences, i.e. life courses. We then use these sensitivities to reveal potential selective forces on the dynamics of life courses. To do so we correlated the sensitivity of each matrix element (stage transition) with respect to the population entropy, to its sensitivity with respect to fitness λ, the population growth rate. Positive correlation between the two sensitivities would suggest that the stage transitions that selection has acted most strongly on (sensitivities with respect to λ) are also those that contributed most to the diversification of life courses. Using an illustrative example on a seabird population, the Thick-billed Murres on Coats Island, that is structured by reproductive stages, we show that the most influential stage transitions for diversification of life courses are not correlated with the most influential transitions for population growth. Our finding suggests that observed diversification in life courses is neutral rather than adaptive. We are at an early stage of understanding how individual level dynamics shape ecological and evolutionary dynamics, and many discoveries await.

scholarly journals Drivers of diversification in individual life courses

2017 ◽  
Author(s):  
Raisa Hernández-Pacheco ◽  
Ulrich K. Steiner
Keyword(s):  
Individual Variability ◽  
Individual Heterogeneity ◽  
Fitness Components ◽  
Evolutionary Mechanisms ◽  
Individual Life ◽  
Structured Population ◽  
Selective Forces ◽  
Life Courses ◽  
Population Entropy ◽  
Stage Composition

ABSTRACTHeterogeneity in life courses among individuals of a population influences the speed of adaptive evolutionary processes, but it is less clear how biotic and abiotic environmental fluctuations influence such heterogeneity. We investigate principal drivers of variability in sequence of stages during an individual’s life in a stage-structured population. We quantify heterogeneity by measuring population entropy, which computes the rate of diversification of individual life courses of a Markov chain. Using individual data of a primate population, we show that density regulates the stage composition of the population, but its entropy and the generating moments of heterogeneity are independent of density. This lack of influence of density on heterogeneity is neither due to low year-to-year variation in entropy nor due to differences in survival among stages, but due to differences in stage transitions. Our analysis thus shows that well-known classical ecological selective forces, such as density regulation, are not linked to potential selective forces governing heterogeneity through underlying stage dynamics. Despite evolution acting heavily on individual variability in fitness components, our understanding is poor whether observed heterogeneity is adaptive and how it evolves and is maintained. Our analysis illustrates how entropy represents a more integrated measure of diversity compared to the population structural composition, giving us new insights about the underlying drivers of individual heterogeneity within populations and potential evolutionary mechanisms.

scholarly journals Drivers of diversity in individual life courses: Sensitivity of the population entropy of a Markov chain

2020 ◽  
Vol 133 ◽  
pp. 159-167 ◽  
Author(s):  
Ulrich K. Steiner ◽  
Shripad Tuljapurkar
Keyword(s):  
Markov Chain ◽  
Individual Life ◽  
Life Courses ◽  
Population Entropy

scholarly journals Evolutionary dynamics of phenotype-structured populations: from individual-level mechanisms to population-level consequences

2016 ◽  
Vol 67 (4) ◽  
Author(s):  
Rebecca H. Chisholm ◽  
Tommaso Lorenzi ◽  
Laurent Desvillettes ◽  
Barry D. Hughes
Keyword(s):  
Evolutionary Dynamics ◽  
Population Level ◽  
Structured Populations ◽  
Individual Level

Determinants of Export Oriented Entrepreneurs from Southeast Europe Region

2018 ◽  
Vol 56 (4) ◽  
pp. 439-452
Author(s):  
Bojan Leković ◽  
Miodrag Petrović ◽  
Nemanja Berber
Keyword(s):  
Early Stage ◽  
New Technology ◽  
Geographical Area ◽  
Southeast Europe ◽  
Social Phenomena ◽  
East Europe ◽  
Individual Level ◽  
International Orientation ◽  
Entrepreneurial Behaviour ◽  
South East Europe

Abstract The subject of this research represents analysis of internationalisation activity of early-stage entrepreneurs in South East Europe region (SEE). The goal of this study is to determine characteristics of export oriented entrepreneurs from SEE region through the study of factors influencing international orientation. Geographical area of this research consists of countries from the South East Europe region. The research sample was formed on the basis of GEM - Global Individual Level Data, covering six countries (Slovenia, Croatia, Hungary, Romania, Bosnia and Herzegovina, and FYR of Macedonia), 12027 respondents of which 645 export-oriented entrepreneurs were identified. Collected data are processed using the software package for statistical analysis. With the help of Ordinal Logistic regression, significant influence of individual factors on the international orientation of entrepreneurs was identified. Research results showed that entrepreneurial motives, entrepreneurial KSA’s, innovation and new technology have a positive relationship with internationalization activity. One of the significant limitations of this paper is the lower Nagelkerk coefficient, which is characteristic for social phenomena. Bearing in mind the fact that this research trying to explain entrepreneurial behaviour, lower coefficients can be very meaningfull.

scholarly journals Interactive effects between travel behaviour and COVID-19: a questionnaire study

2021 ◽  
Author(s):  
Jinbao Zhang ◽  
Jaeyoung Lee
Keyword(s):  
Early Stage ◽  
Travel Behaviour ◽  
Interactive Effects ◽  
Factors Affecting ◽  
Individual Level ◽  
Passenger Volume ◽  
Spatial Autoregressive ◽  
Railway Passenger ◽  
The Individual ◽  
And Control

Abstract This study has two main objectives: (i) to analyse the effect of travel characteristics on the spreading of disease, and (ii) to determine the effect of COVID-19 on travel behaviour at the individual level. First, the study analyses the effect of passenger volume and the proportions of different modes of travel on the spread of COVID-19 in the early stage. The developed spatial autoregressive model shows that total passenger volume and proportions of air and railway passenger volumes are positively associated with the cumulative confirmed cases. Second, a questionnaire is analysed to determine changes in travel behaviour after COVID-19. The results indicate that the number of total trips considerably decreased. Public transport usage decreased by 20.5%, while private car usage increased by 6.4%. Then the factors affecting the changes in travel behaviour are analysed by logit models. The findings reveal significant factors, including gender, occupation and travel restriction. It is expected that the findings from this study would be helpful for management and control of traffic during a pandemic.

Antecedents of growth-oriented entrepreneurship before and during the Greek economic crisis

2017 ◽  
Vol 24 (3) ◽  
pp. 528-544 ◽  
Author(s):  
Ioannis Giotopoulos ◽  
Alexandra Kontolaimou ◽  
Aggelos Tsakanikas
Keyword(s):  
Work Experience ◽  
Early Stage ◽  
New Ventures ◽  
High Growth ◽  
Content Type ◽  
Crisis Period ◽  
Individual Level ◽  
Level Data ◽  
The Social ◽  
Before And After

Purpose The purpose of this paper is to explore potential drivers of high-growth intentions of early-stage entrepreneurs in Greece before and after the onset of the financial crisis of 2008. Design/methodology/approach To this end, the authors use individual-level data retrieved from Global Entrepreneurship Monitor annual surveys (2003-2015). Findings The results show that high-growth intentions of Greek entrepreneurs are driven by different factors in the crisis compared to the non-crisis period. Male entrepreneurs and entrepreneurs with significant work experience seem to be more likely to be engaged in growth-oriented new ventures during the crisis period. The same appears to hold for entrepreneurs who are motivated by an opportunity and also perceive future business opportunities in adverse economic conditions. On the other hand, the educational level and the social contacts of founders with other entrepreneurs are found to drive ambitious Greek entrepreneurship in the years before the crisis, while they were insignificant after the crisis outbreak. Originality/value Based on the concept of ambitious entrepreneurship, this study contributes to the literature by investigating the determinants of entrepreneurial high-growth expectations in the Greek context emphasizing the crisis period in comparison to the pre-crisis years.

scholarly journals Towards a novel design perspective for system vulnerability using a Markov chain

2018 ◽  
Author(s):  
A C Habben Jansen ◽  
E A E Duchateau ◽  
A A Kana
Keyword(s):  
Markov Chain ◽  
Distributed Systems ◽  
Early Stage ◽  
Test Case ◽  
Damage Scenarios ◽  
System Vulnerability ◽  
Residual Capacity ◽  
Design Perspective ◽  
Novel Design ◽  
Different Levels

In order to investigate to which extent naval ships can execute their operational scenario after damage, an early stage assessment of the vulnerability of distributed systems needs to be carried out. Such assessments are currently mostly done by evaluating the performance of predefined concepts. However, such an approach does not necessarily lead to the most desirable solution, since solutions outside the scope of the designer’s preconceived ideas or experience are inherently hard to investigate. This paper therefore proposes several steps towards an approach that enables a vulnerability assessment that is independent of predefined concepts. This is done by incorporating several additions to an existing system vulnerability approach developed by the authors, using a Markov chain. With this approach there is no longer a need for modelling individual hits or damage scenarios. Whereas the approach has previously been shown in concept, this paper introduces three improvements that contribute to the applicability of the approach: 1)it is scaled up in order to model a larger number of compartments and distributed systems, 2) the hit probabilities for different compartments can be adjusted, and 3) it is shown how the availability of main ship functions can be derived from the availability of individual connections. A test case that compares two powering concepts (conventional and full electric powering) of a notional Oceangoing Patrol Vessel (OPV) is provided to illustrate the principles behind the improvements. From the results the two main contributions of this paper can be obtained: 1)the possibility to assess the system vulnerability for different levels of required residual capacity at different impact levels, and 2) and the quantitative nature of the results, aiding ship designers and naval staff with understanding the consequences of various concepts on the system vulnerability. 

scholarly journals Regional Cultural Context as a Determinant of Entrepreneurial Behaviour: The Case of Germany

2020 ◽  
Vol 29 (1) ◽  
pp. 88-118
Author(s):  
Kadri Arrak ◽  
Anneli Kaasa ◽  
Urmas Varblane
Keyword(s):  
Cultural Context ◽  
Positive Impact ◽  
Important Determinant ◽  
Early Stage ◽  
Cultural Dimensions ◽  
Individual Level ◽  
Entrepreneurial Behaviour ◽  
Level Data ◽  
The Impact ◽  
Original Approach

This exploratory article aims to take first steps towards understanding whether a regional cultural background has, among other determinants, an influence on a person’s entrepreneurial behaviour, relying on the example of Germany. A multilevel approach is applied combining the Global Entrepreneurship Monitor individual-level data about entrepreneurship with up-to-date cultural dimensions indicators based on Hofstede’s original approach at the regional (NUTS 1) level. The results indicate that regional cultural context is an important determinant of entrepreneurial behaviour. At that, different cultural dimensions have different impacts, and the impact also differs across different stages of entrepreneurship. A lower level of uncertainty avoidance in a region could have a positive impact on early-stage entrepreneurship, whereas the established business ownership seems to be encouraged by a lower level of power distance.

ENTREPRENEURIAL ACTIVITY IN AMERICAN INDIAN NATIONS: EXTENDING THE GEM METHODOLOGY

2013 ◽  
Vol 18 (02) ◽  
pp. 1350009
Author(s):  
REBECCA J. FRANKLIN ◽  
MICHAEL H. MORRIS ◽  
JUSTIN W. WEBB
Keyword(s):  
American Indian ◽  
Early Stage ◽  
The United States ◽  
Entrepreneurial Activity ◽  
Global Entrepreneurship Monitor ◽  
Nascent Entrepreneurship ◽  
Individual Level ◽  
Global Entrepreneurship ◽  
Entrepreneurial Activities ◽  
Indian Nations

Drawing on institutional theory and using a methodology adapted from the Global Entrepreneurship Monitor (GEM), early stage entrepreneurial activities are examined within American Indian nations. Examining a context within a larger institutional context, comparisons are made between three American Indian nations and the United States. Patterns are identified regarding total entrepreneurial activity (TEA), nascent entrepreneurship, business discontinuation and new and established business rates. Additional analyses are conducted of individual-level variables within American Indian nations including location, self-efficacy and other variables in relation to nascent entrepreneurship and business ownership. Implications are drawn for tribal entrepreneurship development and further extension of the GEM methodology.

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