Mixture cure model with an application to interval mapping of quantitative trait loci

When censored time-to-event data are used to map quantitative trait loci (QTL), the existence of nonsusceptible subjects entails extra challenges. If the heterogeneous susceptibility is ignored or inappropriately handled, we may either fail to detect the responsible genetic factors or find spuriously significant locations. In this article, an interval mapping method based on parametric mixture cure models is proposed, which takes into consideration of nonsusceptible subjects. The proposed model can be used to detect the QTL that are responsible for differential susceptibility and/or time-to-event trait distribution. In particular, we propose a likelihood-based testing procedure with genome-wide significance levels calculated using a resampling method. The performance of the proposed method and the importance of considering the heterogeneous susceptibility are demonstrated by simulation studies and an application to survival data from an experiment on mice infected with Listeria monocytogenes.     

Can skill-biased technological change compress unemployment rate differentials across education groups?

Our aim is to explain why the pattern of relative unemployment rates by education groups was non monotonic in most of the OECD countries. In a two-sector matching model, a simple unexpected productivity shock biased against unskilled labor can replicate the observed dynamics. Demographic effects of skill-biased shocks can be related to inequality in the distribution of wealth. Received: 27 April 1999/Accepted: 08 June 2000     

Pareto improving transition from a pay-as-you-go to a fully funded pension system in a model of endogenous growth

In this paper we investigate the possibility of Pareto improving social security reforms within a framework of endogenous growth. Belan et al. (1998) propose a transition from a pay-as-you-go (PAYG) pension system to a system of savings–subsidization. We follow this approach and prove that a Pareto improving conversion from the PAYG system to a fully funded one is possible. Finally, we compare the subsidy system with the fully funded system and discuss the problem of implementing the transition to the fully funded system. Received: 07 March 1999/Accepted: 13 December 1999     

The allocation of time and goods in household activities: A test of separability

In this paper, we test for the weak separability hypothesis imposed by the household production model between goods and time inputs used in the production of different commodities. Our data come from a French survey which reports both expenditures and time that households devote to some activities. The results allow us to show that the weak separability assumption cannot be rejected only when households are strongly time constrained. In the opposite case, home time uses are found to be nonseparable. Received: 24 November 1999/Accepted: 16 November 2000     

Labor immigration and long-run welfare in a growth model with heterogenous agents and endogenous labor supply

This paper examines the consequences of labor immigration in an OLG economy in which agents have an elastic labor supply and differ with respect to degrees of altruism and rates of time preference. It focuses on three substantive questions. First, how do immigrants influence the bequest motive of altruistic natives? Second, what impact do immigrants have on the labor supply of natives? Finally, how does immigration affect the long-run welfare of both altruistic and non altruistic natives? Received: 25 November 1999/Accepted: 07 April 2000     

Declining employment success of immigrant males in Sweden: Observed or unobserved characteristics?

Focusing on Nordic and Yugoslavian immigrant males, we study the determinants of employment success of natives and immigrants in Sweden. Furthermore, we investigate the reasons behind the arising gap in employment success between Swedes and immigrants from 1970 to 1990. In a decomposition analysis, we find that the main part of the decline in the employment probability of immigrants relative to Swedes over time is explained by a change in coefficients (unobserved characteristics) rather than a change in determinants (observed characteristics). Received: 22 June 1998/Accepted: 23 March 2000     

The allocation and value of time assigned to housework and child-care: An analysis for Switzerland

In this paper, data from the 1997 Swiss Labour Force Survey are used to analyse the allocation and value of time assigned to housework and child-care. It is shown that men's allocation of time to housework and child-care is largely invariant to changes in socio-economic factors. Women's allocation of time to housework and child-care, on the other hand, is shown to depend on several social, economic, and demographic factors. The value of time assigned to housework and child-care is calculated with two market replacement cost methods and three opportunity cost methods. The results show that the value of time assigned to housework and child-care ranges from 27% to 39% and from 5% to 8% of GDP (in 1997), respectively. The value of time assigned to housework and child-care is also calculated for different household structures. Received: 15 April 1999/Accepted: 5 May 2000     

世纪之交北京散文创作景象

本文从历时态和共时态的角度 ,对散文老生代现象、作家散文与学者随笔、女性散文和新生代作品进行全面详尽地梳理和品评 ,寻求各种现象流变、文体革新背后的文化依据 ,力图把握多重语名北京散文创作中呈现出的现象流变和多元格局 ,使散文理论的建构介入当下创作     

The economic importance of air travel in high-amenity rural areas

The western United States offers a case study on the importance of access to large population centers and their markets, via road and air travel, for economic development. The vast distances between towns and cities in the American West can be a detriment to business, yet they also serve to attract technology and knowledge-based workers seeking to live in a picturesque setting. In spite of the increasing importance of amenities to migration and business location, also needed is access to markets, particularly via commercial air service. We test a new county classification system for the western United States to reflect differing degrees of access to population centers and account for the increasing importance of airports. Past classifications are based on population size and cross-county commuting. We examine the validity of this new classification and test for differences in economic performance among the three county types. Our findings show that there are three distinct Wests that can be classified using economic performance measures and socioeconomic characteristics. The results show that “metro” and “isolated” counties are clearly distinct, but “connected” counties, those that are rural in nature but have ready access to metropolitan areas via air travel, can be difficult to distinguish from “metro” and “isolated” counties. Much of the variation is explained by travel distance to airports. The findings illustrate the importance of airports in rural development, and the limitations facing those communities that are isolated from markets and population centers. The results apply to other parts of the world with similar characteristics that include large expanses of open space, natural amenities that attract migrants and stimulate new business, and different degrees of access to large population centers via road or air travel, and therefore different rates of economic growth.     

改进的Prim算法在求解旅行商问题中的应用

旅行商问题是图论中一个典型的组合优化问题,它的问题描述与图论中最小生成树问题的描述具有很多相似之处,在一些情形下,可以用最小生成树形成的路径来获得旅行商问题的最短巡回路径。首先给出了最小生成树Prim算法,然后对其算法进行了改进,通过改进的Prim算法成功求解了旅行商问题。