Variance Of Migration Research Articles

The impact of limiting long term illness on internal migration in England and Wales: New evidence from census microdata

Previous research has suggested that poor health is associated with reduced migration; this knowledge stems from models based on past censuses, or longitudinal studies which imply that the factors influencing migration are the same between those in good and poor health. This paper addresses these issues by utilising health-stratified analyses on the 2011 Census Individual Secure Sample for England and Wales. Multilevel models predict the odds of moving for working age adults, controlling for key predictors of migration, estimating the effect of health status on the odds of moving and the destination-specific variance in migration. We find that those in poor health are less likely to move, after controlling for individual level characteristics. In contrast with expectations, economic inactivity, marriage and being in African, Caribbean, Black, Other or Mixed ethnic groups were not significant predictors of migration among the unhealthy sample, but were for the healthy sample. We conclude that migration is health-selective and propose implications for understanding area level concentrations of poor health in England and Wales.

Random genetic drift in a cline

A diffusion model is derived for random genetic drift in a cline. The monoecious organism occupies an unbounded linear habitat with constant, uniform population density. Migration is homogeneous, symmetric, and independent of genotype. The analysis applies to a single diallelic locus without dominance or mutation. Assuming that Hardy-Weinberg proportions obtain locally, partial differential equations are deduced for the expected gene frequency at each location and the covariance between gene frequencies at any two points of the habitat. For most selection gradients, the population density, rho, selection intensity, s, and migration variance, sigma(2), appear only combined in the single dimensionless parameter, beta, the ratio of the characteristic length for migration and random drift to the natural distance for migration and selection. Random drift is highly significant if beta << 1; it causes only relatively small variations of order 1/beta around the deterministic cline if beta >> 1. With beta >> 1, the correlation between the gene frequencies at any two points is very nearly independent of beta, and hence is parameter-free for particular forms of the selection gradient. For a very steep selection gradient, beta = 2 [unk] 2srhosigma, i.e., essentially the product of the square root of the selection intensity and the neighborhood size.

Heterozygosity and relationship in regularly subdivided populations

The problems about regularly subdivided populations (with either finite or infinite number of subdivisions) may be unified by using Fourier or Laplace transforms. It is shown that some general theorems give (in unidimensional and in bidimensional cases) approximate values of: 1. 1. the rate of decrease of heterozygosity when there are no mutations. 2. 2. the rate of decrease of kinship as a function of distance, in the asymptotic stationary situation, when there are mutations towards an allele already existing or towards a new allele. When σ 2, variance of migration in some direction, is sufficiently large with respect to number of subdivisions, it is shown that the population behaves as a wholly panmictic one.

An analysis of the determinants of internal labor mobility in India.

Several variables have been chosen which might reasonably be expected to explain the interstate migration which has occurred in India. The independent variables used in the study explain a fairly high percentage of the variance in migration between states, and all variables except Uj are significant at the 5 percent level or better. The distance variable consistently has in absolute value the highest elasticity in the various estimated relationships, and it is the variable which contributes most in terms of addition to R2. This result is similar to those of other studies dealing with both advanced and less-developed countries, but it appears that the deterring effects of distance may be greater in India than in other countries studied. Migration in India tends to be away from low-income states and toward high-income states, a finding which is similar to those for Ghana, Egypt, and Brazil. Migration also tends to be away from and to populous states, and while migration is away from highly urbanized states, it does not seem to be toward highly urbanized places in India,ceteris paribus. However, migration does tend to be in the direction of places which are urbanizing rapidly and away from places which are urbanizing slowly. There is evidence that in India mobility tends to increase with increased education; this finding is contrary to what was found for Ghana, Egypt, and Brazil. Migration in India also tends to be toward places which display relatively high levels of educational achievement.

The determinants of labor migration in Egypt.

The factors which affect individual decisions with regard to geographic movement in Egypt are examined and the magnitude in which each factor exerts its influence on aggregate geographic labor supply adjustments is estimated. The spatial unit used in the study is the administrative region, of which there are 25. No effort is made to esimate the impact which migration has had on the origin or destination region. The migrant will presumably choose that destination which, given his information, the migrant thinks will be best. The model which is employed attempts to explain gross interregional migration without the explicit introduction of an individual decision function. Rather, migration is related to certain aggregate proxy variables. Among the independent variables employed in the analysis are (origin and destination) income, education, urbanization, and population. The other explanatory variable used is the distance between region i and region j. The migration measure employed refers to cumulative male migration which occurred prior to 1960; the independent variables are defined for a given point in time (1960). The independent variables explain a reasonably large percentage of the variance in migration between regions in Egypt. All variables were significant at the 5% level or better. The findings indicate that distance acts as an important impediment to migration. Migration is away from low wage and toward high wage regions, which may have contributed to a narrowing of regional wage differentials. Migrants are attracted to regions which have large populations and to regions which have a large percentage of urban to total population. A tendency exists for migrants to come from regions with large populations. There is also some tendency for migrants to come from regions which have a relatively large urban population. Migrants do not appear to come from regions with high educational levels.