Economic Development and the Timing and Components of Population Growth

This paper examines the relationship between population growth and economic growth in developing countries from 1965 to 1985. Our results indicate that developing countries were able to shift their labor force from low-productivity agriculture to the higher-productivity industry and service sectors, and to increase productivity within those sectors, despite the rapid growth of their populations. We also find that at given rates of population growth, income growth is related to the time path of population growth and that population growth due to high birth and death rates is associated with slower income growth than population growth due to relatively low birth and death rates. Hence, the timing and components of population growth are important elements in the process of economic development.

The "Youth Problem": Age or Generational Crowding?

This paper attempts to distinguish between two alternative views of the labor market problems faced by young workers in a number of industrialized countries in the 1970s and early 1980s. The first view is that the low relative earnings and high unemployment rates experienced by these workers were largely "age" related. Although this view carries the implication that the problems will disappear for recent youth cohorts as they grow older, it also implies that the problems will be "handed over" to successive waves of youth cohorts as they enter the labor market. The second view is that the labor market problems of recent youth cohorts are a consequence of their large size. This view has very different implications since generational crowding can permanently or temporarily depress the economic position of large cohorts but need not have an adverse effect on later waves of smaller youth cohorts. On the basis of a multicountry empirical analysis of patterns ofcohort size, earnings, unemployment, and the distribution of young workers across industries, we have four main sets of findings to report. First, the baby-boom was not uniformly experienced across OECD economies - in terms of either its timing or magnitude. While some countries, such as Canada, the U.S., and Belgium had large increases in the youth share ofthe population from 1965 to 1980, others, notably Japan and Switzerland, had large decreases. Second, our empirical results indicate that large cohort size tends to have a negative effect on the "expected relative earnings" of the cohort, where expected relative earnings is defined as the product of the earnings and the employment-to-labor force ratio of a young cohort relative to the same product for an older cohort. There is, moreover, a marked trade-off betweenthe relative earnings effect and the relative employment effect with large cohort sizes reducing relative earnings in some countries and reducing reiative employment in others. Third, at least for the U.S., the relatively low wages and high unemployment of the "unlucky cohorts" tend to converge to the patterns that would have resulted had the cohorts been more "normal" in size, with the convergence occurring within a decade or so. Fourth, our results show that baby-boom cohorts were absorbed inthe U.S. and other OECD economies quite evenly across a wide range of industries. This finding contradicts the popular belief that large youth cohorts were absorbed primarily through expansion of those industries that have been traditionally youth-intensive.

Population Growth, Labor Supply, and Employment in Developing Countries

The economies of the less developed countries are about to face perhaps the greatest challenge in their histories: generating a sufficient number of jobs at reasonable wages to absorb their rapidly growing populations into productive employment. In terms of absolute magnitude, this challenge has no precedent in human history. In some respects, this challenge is also unprecedented in terms of its nature, given, on the one hand, the limited availability of natural resources in many countries and, on the other hand,the widespread availability of advanced technology.This paper examines the nature and magnitude of the principal effects of population growth on labor supply and employment in the developing economies of the world. On the supply side of labor markets, we discuss key features of the interrelations between population growth and the labor force. These include the lags between population growth and labor force participation; the independent effects on labor supply of accelerated population growth due to changes in fertility, mortality, and migration; patterns and trends in labor force participation rates; and gender differences in labor supply behavior. On the demand side, we describe and analyze the nature of labor markets in developing economies and attempt to identify the key factors that condition their labor absorption capacity. Descriptive statistics on the characteristics of developing country labor markets and on the relationships between population growth, labor supply, employment shifts, and growth of output per worker are presented and discussed.The key result of our analysis is that, despite the unprecedented magnitude of population growth and the existence of imperfections in labor markets, developing economies tended to shift between 1960 and 1980, from low-productivity agriculture to the higher productivity service and industrial sectors and, albeit with some exceptions, to raise real income per capita. With respect to their prospects for the remainder of this century, we also conclude that Malthusian disasters will not necessarily be the result of forecasted population growth, provided the developing economies can generate human and physical capital investments of comparable relative magnitudes to the past two decades. However, on the basis of past history, the middle-income developing countries are likely to perform better in this respect than the low-income countries, some of whom may need considerable help if they are to absorb increased population while shifting labor to more productive sectors and raising output per worker.

Changes in Earnings Differentials in the 1980s: Concordance, Convergence, Causes, and Consequences

This paper analyzes changes in U.S. earnings differentials in the 1980s between race, gender, age, and schooling groups. There are four main sets of results to report. First, the economic position of less-educated workers declined relative to the more-educated among almost all demographic groups. Education-earnings differentials clearly rose for whites, but less clearly for blacks, while employment rate differences associated with education increased more for blacks than for whites. Second, much of the change in education-earnings differentials for specific groups is attributable to measurable economic factors: to changes in the occupational or industrial structure of employment; to changes in average wages within industries; to the fall in the real value of the minimum wage and the tall in union density; and to changes in the relative growth rate of more-educated workers. Third, the earnings and employment position of white females, and to a lesser extent of black females, converged to that of white males in the 1980s, across education groups. At the same time, the economic position of more-educated black males appears to have worsened relative to their white-male counterparts. Fourth, there has been a sizable college-enrollment response to the rising relative wages of college graduates. This response suggests that education-earnings differentials may stop increasing, or even start to decline, in the near future.

"Changes in Earnings Differentials in the 1980s: Concordance, Convergence, Causes, and Consequence"

This paper analyzes changes in U.S. earnings differentials in the 1980s between race, gender, age, and schooling groups. There are four main sets of results to report. First, the economic position of less-educated workers declined relative to the more-educated among almost all demographic groups. Education-earnings differentials clearly rose for whites, but less clearly for blacks, while employment rate differences associated with education increased more for blacks than for whites. Second, much of the change in education-earnings differentials for specific groups is attributable to measurable economic factors: to changes in the occupational or industrial structure of employment; to changes in average wages within industries; to the fall in the real value of the minimum wage and the fall in union density; and to changes in the relative growth rate of more educated workers. Third, the earnings and employment position of white females, and to a lesser extent of black females, converged to that of white males in the 1980s, across education groups. At the same time, the economic position of more-educated black males appears to have worsened relative to their white-male counterparts. Fourth, there has been a sizable college-enrollment response to the rising relative wages of college graduates. This response suggests that education-earnings differentials may stop increasing, or even start to decline, in the near future.

Astrometric Microlensing Constraints on a Massive Body in the Outer Solar System with Gaia

A body in Solar orbit beyond the Kuiper belt exhibits an annual parallax that exceeds its apparent proper motion by up to many orders of magnitude. Apparent motion of this body along the parallactic ellipse will deflect the angular position of background stars due to astrometric microlensing ("induced parallax"). By synoptically sampling the astrometric position of background stars over the entire sky, constraints on the existence (and basic properties) of a massive nearby body may be inferred. With a simple simulation, we estimate the signal-to-noise for detecting such a body -- as function of mass, heliocentric distance, and ecliptic latitude -- using the anticipated sensitivity and temporal cadences from Gaia (launch 2011). A Jupiter-mass (M_Jup) object at 2000 AU is detectable by Gaia over the whole sky above 5-sigma, with even stronger constraints if it lies near the ecliptic plane. Hypotheses for the mass (~3M_Jup), distance (~20,000 AU) and location of the proposed perturber ("Planet X") which gives rise to long-period comets may be testable.Comment: 17 pages, 6 figures. Figures revised, new figure added, minor text revisions. Accepted to ApJ, to appear in the Dec 10, 2005 issue (v635

Discovery of a supernova associated with GRB 031203: SMARTS Optical-Infrared Lightcurves from 0.2 to 92 days

Optical and infrared monitoring of the afterglow site of gamma-ray burst (GRB) 031203 has revealed a brightening source embedded in the host galaxy, which we attribute to the presence of a supernova (SN) related to the GRB ("SN 031203"). We present details of the discovery and evolution of SN 031203 from 0.2 to 92 days after the GRB, derived from SMARTS consortium photometry in I and J bands. A template type Ic lightcurve, constructed from SN 1998bw photometry, is consistent with the peak brightness of SN 031203 although the lightcurves are not identical. Differential astrometry reveals that the SN, and hence the GRB, occurred less than 300 h_71^-1 pc (3-sigma) from the apparent galaxy center. The peak of the supernova is brighter than the optical afterglow suggesting that this source is intermediate between a strong GRB and a supernova.Comment: 11 pages, 3 figures, submitted to ApJ Letter

Convergence of random zeros on complex manifolds

We show that the zeros of random sequences of Gaussian systems of polynomials of increasing degree almost surely converge to the expected limit distribution under very general hypotheses. In particular, the normalized distribution of zeros of systems of m polynomials of degree N, orthonormalized on a regular compact subset K of C^m, almost surely converge to the equilibrium measure on K as the degree N goes to infinity.Comment: 16 page