David N. Weil

The Baby Boom, the Baby Bust, and the Housing Market

This paper examines the impact of major demographic changes on the housing market in the United States. The entry of the Baby Boom generation into its house-buying years is found to be the major cause of the increase in real housing prices in the 1970s. Since the Baby Bust generation is now entering its house-buying years, housing demand will grow more slowly in the 1990s than in any time in the past forty years. If the historical relation between housing demand and housing prices continues into the future, real housing prices will fall substantially over the next two decades.

Saving and Growth: A Reinterpretation

We examine the relationship between income growth and saving using both cross-country and household data. At the aggregate level, we find that growth Granger causes saving, but that saving does not Granger cause growth. Using household data, we find that households with predictably higher income growth save more than households with predictably low growth. We argue that standard Permanent Income models of consumption cannot explain these findings, but that a model of consumption with habit formation may. The positive effect of growth on saving implies that previous estimates of the effect of saving on growth may be overstated.

Mortality decline, human capital investment, and economic growth

We examine the role of increased life expectancy in raising human capital investment during the process of economic growth. We develop a continuous time, overlapping generations model in which individuals make optimal schooling investment choices in the face of a constant probability of death. We present analytic results, followed by results from a calibrated version of the model using realistic estimates of the return to schooling. Mortality decline produces economically significant increases in schooling and consumption. Allowing schooling to vary endogenously produces a much larger response of consumption and capital to mortality decline than is observed when schooling is held fixed.

Comparison Utility in a Growth Model

We examine the dynamics of two endogenous-growth modelsin which agents have comparison utility. In the inward-lookingeconomy, individuals care about how their current consumptioncompares with their own past consumption. In the outward-lookingeconomy, they care about how their own consumption compares withother people‘s consumption. In response to a negative shock tocapital, saving and growth will temporarily fall in both of themodels that we consider but will remain constant in a model withstandard preferences. The decline will be smaller in the outward-than in the inward-looking case, but utility will be lower inthe former case because of a negative externality.

Population, Technology, and Growth: From the Malthusian Regime to the Demographic Transition

This paper develops a unified model of growth, population, and technological progress that is consistent with long-term historical evidence. The economy endogenously evolves through three phases. In the Malthusian regime, population growth is positively related to the level of income per capita. Technological progress is slow and is matched by proportional increases in population, so that output per capita is stable around a constant level. In the post-Malthusian regime, the growth rates of technology and total output increase. Population growth absorbs much of the growth of output, but income per capita does rise slowly. The economy endogenously undergoes a demographic transition in which the traditionally positive relationship between income per capita and population growth is reversed. In the Modern Growth regime, population growth is moderate and income per capita rises rapidly.

The Saving of the Elderly in Micro and Macro Data

Examination of household (micro) data on the elderly has generally concluded that they do not dissave significantly, whereas estimates using aggregate (macro) data have shown that the presence of a large elderly population leads to a lower saving rate. This paper shows that if interactions between generations are important, one would not expect these estimates to be the same. The paper presents new evidence that bequests are plausibly the source of this discrepancy. Examination of data from young households that have received or expect bequests confirms that bequests are indeed an important factor determining the saving of the young.

When Does Improving Health Raise GDP

We assess quantitatively the effect of exogenous health improvements on output per capita. Our simulation model allows for a direct effect of health on worker productivity, as well as indirect effects that run through schooling, the size and age-structure of the population, capital accumulation, and crowding of fixed natural resources. The model is parameterized using a combination of microeconomic estimates, data on demographics, disease burdens, and natural resource income in developing countries, and standard components of quantitative macroeconomic theory. We consider both changes in general health, proxied by improvements in life expectancy, and changes in the prevalence of two particular diseases: malaria and tuberculosis. We find that the effects of health improvements on income per capita are substantially lower than those that are often quoted by policy-makers, and may not emerge at all for three decades or more after the initial improvement in health. The results suggest that proponents of efforts to improve health in developing countries should rely on humanitarian rather than economic arguments.

How Much of Cross-Country Income Variation is Explained by Health?

We use development accounting techniques to assess the contribution of health to differences in income per capita among countries. Rather than rely on regressions in aggregate data, we build up estimates of the effect of health starting from microeconomic data. We examine both a particular condition, anemia, and a proxy for general health, the adult survival rate. We find that differences in anemia explain 1.3 percent of the log variance of income per capita, and that differences in adult survival explain 19 percent of the log variance of income per capita. The latter figure is almost one third of the variation in output that is left unexplained by other measures of factor accumulation. (JEL: O47, I10) Copyright (c) 2003 The European Economic Association.

Intergenerational earnings mobility, inequality and growth

We examine a model in which per capita income, inequality, intergenerational mobility, and returns to education are all determined endogenously. Individuals earn wages depending on their ability, which is a random variable. They purchase an education with transfers received from their parents, and are subject to liquidity constraints. In the model, multiple steady state equilibria are possible: countries with identical tastes and technologies can reach differing rates of mobility, inequality, and per capita income. Equilibria with higher levels of output also have lower inequality, higher mobility, and more efficient distribution of education.

The baby boom, the baby bust, and the housing market A reply to our critics

This paper explores the impact of demographic changes on the housing market in the US, 1st by reviewing the facts about the Baby Boom, 2nd by linking age and housing demand using census data for 1970 and 1980, 3rd by computing the effect of demand on price of housing and on the quantity of residential capital, and last by constructing a theoretical model to plot the predictability of the jump in demand caused by the Baby Boom. The Baby Boom in the U.S. lasted from 1946-1964, with a peak in 1957 when 4.3 million babies were born. In 1980 19.7% of the population were aged 20-30, compared to 13.3% in 1960. Demand for housing was modeled for a given household from census data, resulting in the finding that demand rises sharply at age 20-30, then declines after age 40 by 1% per year. Thus between 1970 and 1980 the real value of housing for an adult at any given age jumped 50%, while the real disposable personal income per capita rose 22%. The structure of demand is such that the swelling in the rate of growth in housing demand peaked in 1980, with a rate of 1.66% per year. Housing demand and real price of housing were highly correlated and inelastic. If this relationship holds in the future, the real price of housing should fall about 3% per year, or 47% by 2007. The theoretical model, a variation of the Poterba model, ignoring inflation and taxation, suggests that fluctuations in prices caused by changes in demand are not foreseen by the market, even though they are predictable in principle 20 years in advance. As the effects of falling housing prices become apparent, there may be a potential for economic instability, but people may be induced to save more because their homes will no longer provide the funds for retirement.