Demographic shocks: the view from history: discussion

Massimo Livi-Bacci has taken us on a fascinating tour of demographic history. What lessons for developments in the world today can we draw from the story he tells? I will distinguish between three types of lessons, which I call "economic lessons," "demographic lessons," and "cultural/political lessons."Demography ; Economic conditions

Intergenerational Transfers, Aging, and Uncertainty

Research on intergenerational transmission of wealth has pointed to uncertainty -- about the date of one's own death, for example -- as a potential source of significant bequest flows. In this paper I examine the effects of this same uncertainty on the behavior of those who expect to receive bequests. Potential heirs who are prudent will consume less than would be warranted by the size of their expected bequests, and so on average consumption will rise at the age when actual bequests are received. I examine the effect of this uncertainty on the outcome of population aging. Population aging, by changing the relative sizes of the bequeathing generation and those receiving bequests, raises the average size of bequests received and reduces the saving of the bequest-receiving generation. I show that accounting for the effects of uncertainty slows down the reduction in saving that results from population aging.

Population Aging

Population aging is primarily the result of past declines in fertility, which produced a decades long period in which the ratio of dependents to working age adults was reduced. Rising old-age dependency in many countries represents the inevitable passing of this %u201Cdemographic dividend.%u201D Societies use three methods to transfer resources to people in dependent age groups: government, family, and personal saving. In developed countries, families are predominant in supporting children, while government is the main source of support for the elderly. The most important means by which aging will affect aggregate output is the distortion from taxes to fund PAYGO pensions.

Post-1500 Population Flows and the Long Run Determinants of Economic Growth and Inequity

We construct a matrix showing the share of the year 2000 population in every country that is descended from people in different source countries in the year 1500. Using this matrix, we analyze how post-1500 migration has influenced the level of GDP per capita and within-country income inequality in the world today. Indicators of early development such as early state history and the timing of transition to agriculture have much better predictive power for current GDP when one looks at the ancestors of the people who currently live in a country than when one considers the history on that country’s territory, without adjusting for migration. Measures of the ethnic or linguistic heterogeneity of a country’s current population do not predict income inequality as well as measures of the ethnic or linguistic heterogeneity of the current population’s ancestors. An even better predictor of current inequality in a country is the variance of early development history of the country’s inhabitants, with ethnic groups originating in regions having longer histories of agriculture and organized states tending to be at the upper end of a country’s income distribution. However, high within-country variance of early development also predicts higher income per capita, holding constant the average level of early development.Economic Growth; Migration; Income Inequality; State History; Linquistic Distance

The Economic Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States

Iodine deficiency is the leading cause of preventable mental retardation in the world today. Iodine deficiency was common in the developed world until the introduction of iodized salt in the 1920’s. The incidence of iodine deficiency is connected to low iodine levels in the soil and water. We examine the impact of salt iodization in the US by taking advantage of this natural geographic variation. Areas with high pre-treatment levels of iodine deficiency provide a treatment group which we can compare to a control group of low iodine deficiency areas. In the US, salt was iodized over a very short period of time around 1924. We use previously unused data collected during WWI and WWII to compare outcomes of cohorts born before and after iodization, in localities that were naturally poor and rich in iodine. We find evidence of the beneficial effects of iodization on the cognitive abilities of the cohorts exposed to it

The Dynamics of the Age Structure, Dependency, and Consumption

We examine the dynamic interaction of the population age structure, economic dependency, and fertility, paying particular attention to the role of intergenerational transfers. In the short run, a reduction in fertility produces a %u201Cdemographic dividend%u201D that allows for higher consumption. In the long run, however, higher old-age dependency can more than offset this effect. To analyze these dynamics we develop a highly tractable continuous-time overlapping generations model in which population is divided into three groups (young, working age, and old) and transitions between groups take place in a probabilistic fashion. We show that most highly developed countries have fertility below the rate that maximizes steady state consumption. Further, the dependency-minimizing response to increased longevity is to raise fertility. In the face of the high taxes required to support transfers to a growing aged population, we demonstrate that the actual response of fertility will likely be exactly the opposite, leading to increased population aging.

Mortality Change, the Uncertainty Effect, and Retirement

We examine the role of changing mortality in explaining the rise of retirement over the course of the 20th century. We construct a model in which individuals make labor/leisure choices over their lifetimes subject to uncertainty about their date of death. In an environment in which mortality is high, an individual who saved up for retirement would face a high risk of dying before he could enjoy his planned leisure. In this case, the optimal plan is for people to work until they die. As mortality falls, however, it becomes optimal to plan, and save for, retirement. We simulate our model using actual changes in the US life table over the last century, and show that this “uncertainty e ect” of declining mortality would have more than outweighed the “horizon e ect” by which rising life expectancy would have led to later retirement. One of our key results is that continuous changes in mortality can lead to discontinuous changes in retirement behavior.uncertainty, retirement