T HIS study attempts to explore the causes of internal migration in Colombia. Migration rates are first estimated for various groups in the population to clarify who migrates and to where. A model of interregional migration is then set forth and estimated for a sample of Colombian municipalities, from which we can infer the responsiveness of migration to some economic, demographic and political developments in the rural and urban sectors of the society.

CLASSIC studies by Kuznets have found that in more developed countries the size distribution of income among persons and among families has become less unequal during the twentieth century [15, 16]. The significance and magniture of this secular equalization of personal incomes can be estimated from time series only when cyclical behavior of the distribution of income is statistically separated from secular trend.' A purpose of this investigation is to propose an aggregate model that incorporates cyclical factors that are hypothesized to displace the distribution of income from its secular or equilibrium trend. Annual personal income data for the Netherlands are used to estimate the model and test the hypotheses implicit in it. The following conclusions emerge: (1) income inequality has decreased markedly in the Netherlands during the last fifty years; (2) secular equalization of incomes stems from the inseparable effects of the increased labor share of income and its more equal distribution; (3) the secular trend is stronger when variation in income associated with age and sex characteristics of the population are eliminated; (4) aggregate disequilibrium in factor markets that induce cyclical change in price and employment levels appears to account for much of the behavior of income inequality; (5) the distributional effect of changes in the price level has reversed and the effect of change in labor productivity has increased in the period since the Second World War.

The analytical framework of this study focuses on several conceptual variables for which empirical counterparts are not readily available: the death of children; the economic resources of the family that grow out of the efforts of husband, wife, and child, each of whose contribution affects differently the relative attractiveness of children; the educational system that has a direct bearing on the cost of rearing children, influences the achievement goals parents set for their offspring, and may also explain differential access to modern methods of birth control; and finally, the web of social and public policies that shape the function of the family and the role of children therein, altering the costs and benefits of rearing a large or small number of children. (Author)

The household production literature emphasizes that technical or biological processes condition input selection by households in their production activities, along with prices and income. Exogenous variations in health, to the extent that they are perceived by individuals (heterogeneity), lead to correlations between inputs and health outcomes that cannot be used to derive causal conclusions. Therefore, estimates of health technology must be obtained from a behavioral model in which health inputs are themselves choices. Consistent estimates are reported of the effect of endogenous inputs, such as medical care, smoking, and fertility, on birth weight and fetal growth in the presence of health heterogeneity.