A New Perspective on Population Ageing.

In Sanderson and Scherbov (2005) we introduced a new forwardlooking definition of age called “prospective age” and argued that its use, along with the traditional backward-looking concept of age, provides a more informative basis upon which to discuss population ageing. Age is a measure of how many years a person has already lived. Everyone of the same age has lived the same number of years. In contrast, prospective age is concerned about the future. Everyone with the same prospective age has the same expected remaining years of life. In this paper, we first explore the concept of prospective age in detail and show, using an analytic formulation, historical data, and forecasts, that prospective age is, in most cases, insensitive to whether it is measured using period or cohort life tables. We, then, use the two age concepts in concert and demonstrate how this enriches our understanding of population ageing in developed countries since 1960.

A new perspective on population aging

In Sanderson and Scherbov (2005) we introduced a new forward-looking definition of age and argued that its use, along with the traditional backward-looking concept of age, provides a more informative basis upon which to discuss population aging. Age is a measure of how many years a person has already lived. In contrast, our new approach to measuring age is concerned about the future. In this paper, we first explore our new age measure in detail and show, using an analytic formulation, historical data, and forecasts, that it is, in most cases, insensitive to whether it is measured using period or cohort life tables. We, then, show, using new forward-looking definitions of median age and the old age dependency ratio, how combining the traditional age concept and our new one enhances our understanding of population aging.age/aging, historical demography, life expectancy, median age, population forecasting, prospective age

A Dynamic Model of Retirement and Social Security Reform Expectations: A Solution to the New Early Retirement Puzzle

The need for Social Security Reform in the next years is hardly a matter of debate. Therefore, the widespread believe among Americans that Social Security will not be able to pay benefits in the long run at the level that was anticipated, does not come as a surprise. The government acknowledges the situation, and predicts that substantial benefits cuts will be necessary, yet no legislation has been passed to tackle the problem. Researchers, however, have rarely modeled the uncertainty over Social Security reform and benefit levels, and how they affect claiming behavior and retirement. The purpose of this paper is to assess the extent to which these perceptions of future cuts might explain the puzzle of earlier take-up despite bigger penalties to doing so in the presence of increasing longevity. By introducing a small amount of uncertainty (based on self-reported responses to questions regarding expectations over future cuts) of a relatively small cut (compared with what the government reports as necessary to solve the crisis) in a dynamic life-cycle model of retirement, we are able to match the claiming behavior observed in the data, without relying on heterogeneous preferences. Our results support the hypothesis that expectations over future benefits are affecting current behavior. We find that a mis-specified dynamic retirement model would erroneously predict that an increase in the NRA would delay claiming behavior and increase labor supply at older ages. Once the appropriate earnings test incentives are modeled, and we account for the probability of reforms to the system, an increase in the NRA has little effect on claiming behavior, and it can even increase the proportion of individuals claiming before the NRA.

What Happened During the Baby Boom? New Estimates of Age and Parity: Specific Birth Probabilities for American Women

It is the main purpose of this paper to examine in detail the pattern of fertility fluctuations in the United States since the Second World War and to define, with some precision, the questions these patterns raise for students of fertility behavior.

Economic Theories of Fertility: What do They Explain?

This working paper is a draft of a chapter in a larger manuscript which is concerned with the time series variations in fertility in the United States since 1920. This chapter asks how economic models of fertility aid our understanding of our demographic history. Thus little attention is given here to the suitability of economic models for the explanation of cross-sectional fertility differentials.

The Effects of Age Structure on Economic Growth: An Application of Probabilistic Forecasting in India

During recent years there has been an increasing awareness of the explanatory power of demographic variables in economic growth regressions. We estimate a new model of the effects of age structure change on economic growth. We use the new model and recent probabilistic demographic projections for India to derive the uncertainty of predicted economic growth rates caused by the uncertainty in demographic developments.Economic growth, age structure, probabilistic demographic projections, India

Faster Increases in Human Life Expectancy Could Lead to Slower Population Aging

Counterintuitively, faster increases in human life expectancy could lead to slower population aging. The conventional view that faster increases in human life expectancy would lead to faster population aging is based on the assumption that people become old at a fixed chronological age. A preferable alternative is to base measures of aging on people's time left to death, because this is more closely related to the characteristics that are associated with old age. Using this alternative interpretation, we show that faster increases in life expectancy would lead to slower population aging. Among other things, this finding affects the assessment of the speed at which countries will age