Tubulins in C. elegans

The C. elegans tubulin family is composed of nine α-, six β-, and one γ-tubulin. Tubulins are highly conserved, functioning as α-β heterodimers that assemble into microtubules. These cylindrical and ubiquitous components of the cytoskeleton are critical for nearly all cellular and developmental processes. C. elegans has provided a model for the study of microtubules in multiple settings including separation of chromosomes, cellular polarity, and neuronal sensation. Tubulins and microtubules interact with a long list of other cellular proteins that regulate tubulin homeostasis, modify microtubule dynamics, and control incorporation into or disassociation of higher-order cellular structures such as spindles or ciliary axonemes. A collection of enzymes modifies tubulins, often at the variable carboxyl-terminal tail, adding another layer of regulation to microtubule structure and function. Genetic and cytological studies in C. elegans have revealed roles for tubulin and its associated proteins in numerous contexts from embryogenesis to adult behavior

Estimating the Family Labor Supply Functions Derived from the Stone-Geary Utility Function

The Stone-Geary utility function defined over an index of goods, the leisure of the husband, and the leisure of the wife is used to derive the earnings functions of the husband and the wife. The parameters of the utility function are estimated from the parameters of the earnings functions in a way that accounts for a number of theoretical and statistical problems. The effect of family composition on utility is estimated by specifying and estimating adult equivalents in consumption and leisure of various categories of children. On the statistical side the following difficulties are all considered: nonlinear constraints across equations, endogenous marginal income tax rates, variations in tastes in the population, heteroscedasticity, and truncation of the left-hand variable. The data come from the 1967 Survey of Economic Opportunity. The results are generally good and support the view that the effects of family composition on utility can be estimated from behavioral relationships. Alternative results that ignore the complicated statistical problems are presented; they imply that the statistical problems are empirically important and should not be ignored.

Savings and Bequests

Empirical studies have indicated that the elderly seem to accumulate wealth after retirement, and that the desire to leave bequests is an important determinent of saving behavior, both kinds of results have cast doubt on the validity of the life cycle hypothesis of consumption. In the first part of this paper, a model of bequests is specified, and the implications for consumption and wealth trajectories are derived. The main result is that, even with a bequest motive, consumption generally decreases with age after retirement, and that wealth will also decrease for all but wealthy households. In the empirical part of the paper, wealth changes of retired households are reported over 10 years of panel data. Contrary to many results from cross-section data, the elderly do dissave: over 10 years the wealth of the elderly in the sample decreases by about 27 real. A test for a bequest motive is proposed. There is no evidence whatsoever for abequest motive.

The Joint Retirement Decision of Husbands and Wives

The objective of the paper is to find empirically whether husbands and wives tend to retire at the same time, and to give an explanation of the findings. Similarity of retirement dates could be caused by similarity of tastes (assortative mating), by economic variables, or by the complimentarity of leisure. Each explanation would have different implications for the response of retirement to policy changes. Both simple data analysis and economic models of the age of retirement point to coordination of retirement dates: husbands and wives tend to retire at the same time. According to the results, very little of the coordination is due to economic variables, and simple cross-tabulations rule out assortative mating as an important explanation. This leaves complimentarity of leisure. Because of data limitations, this conclusion is, however, mainly qualitative. The data set is the Mew Beneficiary Survey.

The Effects of Demographic Trends on Consumption, Saving and Government Expenditures in the U.S.

This paper reviews and analyzes forecasts of the Social Security trust funds, government spending, medical expenditures, and other elements of aggregate income and spending. According to these forecasts, the aging of the U.S. population will require some increases in taxes to support the retirement system. It should reduce the saving rate, and the composition of output will change. By themselves, these changes seem manageable. However, the direct effects of aging are completely dominated by the projected increases in medical expenditures. Although medical costs interact with aging, most of the increases are not related to aging. Even the moderately high forecast of medical spending will require that all increases in output between now and 2020 be devoted to the consumption of medical services, allowing no increase in any other component of consumption.

The Effects of the Financial Crisis on Actual and Anticipated Consumption

We studied how households adjust their spending in response to the financial crisis. Based on five waves of data from the Consumption and Activities Mail Survey, we quantified the reduction in total consumption and in specific categories of consumption in the older population at large and by stock ownership, both as a proxy for wealth and to test assumptions about whether stock ownership was associated with different responses. In particular, we compared consumption changes between 2007 and 2009 with consumption changes over prior years. We used panel data on anticipated changes in spending at retirement to quantify the effects of the financial crisis on well-being in retirement via a difference-in-differences approach.

Economic Well-Being at Older Ages: Income- and Consumption-Based Poverty Measures in the HRS

According to economic theory, well-being or utility depends on consumption. However, at the household level, total consumption is rarely measured because its collection requires a great deal of survey time. As a result income has been widely used to assess economic well-being and poverty rates. Yet, because households can use wealth to consume more than income, an income-based measure of well-being could yield misleading results for many households, especially at older ages. We use data from the Health and Retirement Study to find income-based poverty rates which we compare with poverty rates as measured in the Current Population Survey. We use HRS consumption data to calculate a consumption-based poverty rate and study the relationship between income-based and consumption-based poverty measures. We find that the poverty rate based on consumption is lower than the income-based poverty rate. Particularly noteworthy is the much lower rate among the oldest single persons such as widows. The explanation for the difference is the ability to consume out of wealth.

Evaluation of Subjective Probability Distributions in the HRS

In the Health and Retirement Survey respondents were asked about the chances they would live to 75 or to 85, and the chances they would work after age 62 or 65. We analyze the responses to determine if they behave like probabilities, if their averages are close to average probabilities in the population, and if they have correlations with other variables that are similar to correlations with actual outcomes. We find that generally they do behave like probabilities and they do aggregate. Most remarkable, however, is that they covary with other variables in the same way actual outcomes vary with the variables. For example, smokers give lower probabilities of living to 75 than nonsmokers. We conclude that these measures of subjective probabilities have great potential use in models of intertemporal decision making under uncertainty.

The Effect of the Risk of Out-of-Pocket Spending for Health Care on Economic Preparation for Retirement

After retirement, the primary sources of uncertainty with respect to an individual’s economic status are longevity, investment outcomes and out-of-pocket spending on health care. In previous work, we estimated economic preparation for retirement, taking into account the risk of living to an advanced old age and the concomitant risk of running out of resources. But while we accounted for the average level out-of-pocket spending for health care, we did not account for the risk of out-of-pocket spending. In this paper we augment our model for this omission. We find that the risk of out-of-pocket health care spending reduces economic preparation for retirement from about 72% of persons in the age range 65-69 to about 63%. However, this relatively modest reduction is quite unequally distributed: about 57% of single persons are adequately prepared when health care spending is not stochastic, but just 44% when it is. Among single women who are not high school graduates the percentage adequately prepared declines from 33% to 15%.