Modeling distances between humans using Taylor’s law and geometric probability

Taylor’s law states that the variance of the distribution of distance between two randomly chosen individuals is a power function of the mean distance. It applies to the distances between two randomly chosen points in various geometric shapes, subject to a few conditions. In Réunion Island and metropolitan France, at some spatial scales, the empirical frequency distributions of inter-individual distances are predicted accurately by the theoretical frequency distributions of inter-point distances in models of geometric probability under a uniform distribution of points. When these models fail to predict the empirical frequency distributions of inter-individual distances, they provide baselines against which to highlight the spatial distribution of population concentrations.     

The Shag‐Band Menace: Tracing the Spread of a Contemporary Legend

The internet enables analysts to better track rumors and contemporary legends through time and space. Comments about sex bracelets reveal waves of concentrated attention; the spread of particular variants display a similar pattern. The diffusion of such stories reflects constructions of childhood and adolescent sexuality as social problems.     

Determinants of International Migration Flows to and from Industrialized Countries: A Panel Data Approach Beyond Gravity1

We quantified determinants of international migratory inflows to 17 Western countries and outflows from 13 of these countries between 1950 and 2007 in 77,658 observations from multiple sources using panel-data analysis techniques. To construct a quantitative model that could be useful for demographic projection, we analyzed the logarithm of the number of migrants (inflows and outflows separately) as dependent variables in relation to demographic, geographic, and social independent variables. The independent variables most influential on log inflows were demographic [log population of origin and destination and log infant mortality rate (IMR) of origin and destination] and geographic (log distance between capitals and log land area of the destination). Social and historical determinants were less influential. For log outflows from the 13 countries, the most influential independent variables were log population of origin and destination, log IMR of destination, and log distance between capitals. A young age structure in the destination was associated with lower inflows while a young age structure in the origin was associated with higher inflows. Urbanization in destination and origin increased international migration. IMR affected inflows and outflows significantly but oppositely. Being landlocked, having a common border, having the same official language, sharing a minority language, and colonial links also had statistically significant but quantitatively smaller effects on international migration. Comparisons of models with different assumed correlation structures of residuals indicated that independence was the best assumption, supporting the use of ordinary-least-squares estimation techniques to obtain point estimates of coefficients.     

Semiparametric estimation of employment duration models

There are a variety of economic areas, such as studies of employment duration and of the durability of capital goods, in which data on important variables typically are censored. The standard techinques for estimating a model from censored data require the distributions of unobservable random components of the model to be specified a priori up to a finite set of parameters, and misspecification of these distributions usually leads to inconsistent parameter estimates. However, economic theory rarely gives guidance about distributions and the standard estimation techniques do not provide convenient methods for identifying distributions from censored data. Recently, several distribution-free or semiparametric methods for estimating censored regression models have been developed. This paper presents the results of using two such methods to estimate a model of employment duration. The paper reports the operating characteristics of the semiparametric estimators and compares the semiparametric estimates with those obtained from a standard parametric model.     

Contract Length as Risk Management When Labor is not Homogeneous

This paper examines the choice of contract length for workers who possess unique skills. Uncertainty, facing both the worker and the firm, creates an incentive to reallocate risk. The uncertainty arises from two sources: variation in the market value of the worker's human capital and fluctuation in the worker's physical production. Long‐term contracts are typically modeled as compensating wage differentials, or as a solution to the problem of asymmetric information. This paper develops a model proposing more complex behavior in the reallocation of risk between the contracting parties. The model shows that long‐term labor contracts are most likely to be observed when price uncertainty in the labor market exceeds the worker's productive uncertainty.     

Pathways to social value and social change: An integrative review of the social entrepreneurship literature

Social entrepreneurship has emerged as an important means of addressing grand challenges. Although research on the topic has accelerated, scholars have yet to articulate an overarching framework that links the different pathways taken by social entrepreneurs with the positive effects of these efforts. To address this shortcoming, we conducted a systematic literature review which enabled us to conceptually differentiate between social value and social change as distinct outcomes of social entrepreneurship and identify seven pathways for achieving these outcomes. Building on our analysis, we outline a research agenda for questions pertaining to: the dynamics between social value and social change; how contextual factors and social entrepreneurs influence various pathways; design principles of business models and innovations that facilitate social value and social change; and defining, measuring, and ensuring accountability for social value and social change.     

Evaluation of treatment programs for persons with severe mental illness: moderator and mediator effects

This study evaluated several statistical models for estimating treatment effects in a randomized, longitudinal experiment comparing assertive community treatment (ACT) versus brokered case management (BCM). In addition, mediator and moderator analyses were conducted. The ACT clients had improved outcomes in terms of housing and psychiatric symptoms than BCM clients. Case management housing assistance and financial assistance partially mediated housing outcomes. No reliable mediators were found for psychiatric symptoms, and no reliable moderators were found for either housing or psychiatric symptoms. The study also made several important methodological advances in the analysis of longitudinal data in randomized experiments.