Non-linear mixed logit

We develop an extension of the familiar linear mixed logit model to allow for the direct estimation of parametric non-linear functions defined over structural parameters. Classic applications include the estimation of coefficients of utility functions to characterize risk attitudes and discounting functions to characterize impatience. There are several unexpected benefits of this extension, apart from the ability to directly estimate structural parameters of theoretical interest.     

Pseudo-observations for competing risks with covariate dependent censoring

Regression analysis for competing risks data can be based on generalized estimating equations. For the case with right censored data, pseudo-values were proposed to solve the estimating equations. In this article we investigate robustness of the pseudo-values against violation of the assumption that the probability of not being lost to follow-up (un-censored) is independent of the covariates. Modified pseudo-values are proposed which rely on a correctly specified regression model for the censoring times. Bias and efficiency of these methods are compared in a simulation study. Further illustration of the differences is obtained in an application to bone marrow transplantation data and a corresponding sensitivity analysis.     

Social mobility in 20 modern societies: The role of economic and political context

It is commonly argued that social mobility rates are influenced by economic and political conditions. Nevertheless, research on this issue has tended to be hindered by two limitations that make it difficult to draw strong conclusions about contextual effects: (1) seldom have country-level and individual-level influences been tested simultaneously, and (2) only rarely have data more recent than the 1970s been employed. We improve on previous research by employing multilevel models fitted to relatively recent survey data collected from 20 modern societies by the International Social Survey Program (ISSP) and national-level characteristics derived from various official sources. Our findings demonstrate systematic cross-national variation in the association between the occupational status of respondents and their fathers. Consistent with the industrialization thesis, this variation is positively associated with per-capita GDP, suggesting that more affluent nations are characterized by more open and fluid stratification structures. Our results also suggest the importance of political regimes and migration for social mobility. In contrast, economic inequality appears to explain very little of the cross-national variation in mobility rates.     

An Improved Approximation to the Exact Solution of the Two-Stage Clonal Growth Model of Cancer

Multistage clonal growth models are of interest for cancer risk assessment because they can explicitly incorporate data on cell replication. Both approximate and exact formulations of the two stage growth model have been described. The exact solution considers the conditional probability of tumors arising in previously tumor-free animals; the approximate solution estimates total probability of tumor formation. The exact solution is much more computationally intensive when time-dependent cell growth parameters are included. The approximate solution deviates from the exact solution at high incidences and probabilities of tumor. This report describes a computationally tractable,'improved approximation'to the exact solution. Our improved approximation includes a correction term to adjust the unconditional expectation of intermediate cells based on the time history of formation of intermediate cells by mutation of normal cells (recruitment) or by cell division in the intermediate cell population (expansion). The improved approximation provided a much better match to the exact solution than the approximate solution for a wide range of parameter values. The correction term also appears to provide insight into the biological factors that contribute to the variance of the expectation for the number of intermediate cells over time.     

Effect of Marriage and Spousal Criminality on Recidivism

The authors analyzed whether the effect of marriage on recidivism varied by spousal criminality. For this purpose, they used propensity score matching and full population data from Statistics Denmark on all unmarried and previously convicted men from birth cohorts 1965–1985 (N = 102,839). The results showed that marriage reduced recidivism compared to nonmarriage only when the spouse had no criminal record. Similarly, marriage to a nonconvicted spouse reduced recidivism significantly more than marriage to a convicted spouse. These findings not only underline how important marriage is for social integration but also stress the heterogeneous nature of the protective effects of marriage.     

Optimal PPS Sampling with Vanishing Auxiliary Variables – with Applications in Microscopy

Recently, non‐uniform sampling has been suggested in microscopy to increase efficiency. More precisely, proportional to size (PPS) sampling has been introduced, where the probability of sampling a unit in the population is proportional to the value of an auxiliary variable. In the microscopy application, the sampling units are fields of view, and the auxiliary variables are easily observed approximations to the variables of interest. Unfortunately, often some auxiliary variables vanish, that is, are zero‐valued. Consequently, part of the population is inaccessible in PPS sampling. We propose a modification of the design based on a stratification idea, for which an optimal solution can be found, using a model‐assisted approach. The new optimal design also applies to the case where ‘vanish’ refers to missing auxiliary variables and has independent interest in sampling theory. We verify robustness of the new approach by numerical results, and we use real data to illustrate the applicability.     

美国政府监管程序的宪法基础

美国今天的政府监管并没有明确的宪法根据。因此,行政程序遭遇到一系列严肃的质问:诸如正当性、公平性和可问责性。不过,在这三个问题上,已经发展出在功能上相当于宪法保障的体制。立法委代的假定应对了正当性难题,行政法发达的制度应对了公平性难题,司法和立法对行政程序众多正式和非正式的控制应对了问责难题。由此产生的图景并非整齐划一、逻辑严密,不过,它是一个可以运作的但却不甚稳定的解决办法,让宪法适应于其制定者不可能预见到的环境。     

Does One Municipality Fit All?The Employment of Refugees in Norway Across Municipalities of Different Centrality and Size

European Journal of Population - Refugees coming to Norway are assigned to a municipality where they start their integration process. These municipalities offer very different contexts for...