تجزیه و تحلیل اقتصادی از امید به زندگی بر حسب جنسیت و کاربرد آن در ایالات متحده آمریکا

This paper presents an economic model to explain the behavior of life expectancy of both sexes. It explicitly examines the relationship between the gender gap in life expectancy and the gender gap in pay. It shows that as the latter narrows over the course of economic development, the former may initially expand but will eventually shrink. Simulation results from our model accord with the behavior of life expectancy for both sexes since the 1940s in the United States

Longevity reflects the quality of life and well being of a society. Over the past century, there has been continuous growth in life expectancy at birth around the world. The significant improvement in longevity is a result of better living and working environments, maternal and preventative care, educated populations, and higher incomes, among other factors. With rare exceptions, women persistently live longer than men. The situation in the United States provides an interesting example. On the one hand, women have always lived longer than men in the US. On the other, both male and female life expectancies have risen greatly, but the difference between the two exhibits both an increasing and declining pattern. Such patterns, as depicted in Fig. 1 and Fig. 2, allow us to study life expectancy in its entirety.1Life expectancy at birth for the whole population in the US rose from 67.2 years in 1948 to 76.7 years in 1998. The gender gap in life expectancy widened between 1948 and 1975, from 5.3 to 7.8 years. In 1979, however, the gap began to narrow, and has continued to narrow from an initial 7.8 to 5.8 years in 1998. For the past two decades, life expectancy for men grew much faster than for women. One explanation, offered by Waldron (1976), for the expanding gap prior to the 1970s was the increase over the same period in male mortality due to ischemtic heart disease and lung cancer, both of which were related to cigarette smoking among men. However, in the late 1970s mortality due to lung cancer rose among women. At the same time, there was a decrease in heart disease mortality among men. Hence, the drop in the life expectancy gap suggests behavioral changes between the two sexes. The gender differential in longevity has for many years been a subject of interest for social scientists. Sociologists and anthropologists explain the differential by adopting the evolutionary theory of sexual selection against a socio-cultural background (Carey and Loperato, 1995). Epidemiologists explore the relationship between life expectancy and socio-economic factors, such as wealth inequality and social status by gender (Wilkinson, 1996). Medical professionals approach the issue by investigating gender-differentiated medical technologies and human biology. For instance, Perls and Fretts (1998) emphasize the unique role of the menopause in female longevity. In this paper, we attempt to offer an economic explanation for the behavior of life expectancy by gender without relying on the types of consumption detrimental to health, such as cigarette smoking, and diseases contracted by men and women, such as cancer. We focus on two questions: why do women live longer than men? And what explains the rise and decline in the life expectancy gap in the United States between 1948 and the present? These questions are not only interesting in their own right but are also practically relevant because the evolution of gender life expectancy can lead to a different scale and composition of the aging population. Lakdawalla and Philipson (2002), for example, provide evidence that a narrowing gender gap in longevity will increase the supply of spousal care, and thus lower the demand for market elderly care. Hence, understanding the relationship between the health statuses of both sexes and the process of economic development may provide important information for health policy regarding care of the elderly. How economic development affects life expectancy remains largely unexplored among economists. Studies on economic growth and development have often treated life expectancy as an exogenous parameter. For instance, Barro (1997) and Barro and Sala-i-Martin (1995) found that life expectancy has a positive effect on economic growth when income is low, and that the effect diminishes for high-income levels. Similarly, Zhang et al. (2001) examined the impact of mortality decline on long-term growth. Ehrlich and Lui (1991) considered the role of intergenerational trade in channeling the effect of exogenous changes in life expectancy on growth and fertility. Kalemli-Ozcan et al. (2000) considered the response of human capital investment to rising longevity in a growth model. In these papers, however, economic agents have no influence over their own longevity. Economic investigations on longevity, e.g. Grossman (1972) and Ehrlich and Chuma (1990), on the other hand, were largely conducted in partial equilibrium models with an exogenous sequence of prices. Also, in these studies health production was usually not addressed at a household level. Although Jacobson (2000) and Bolin et al. (2001) did indeed consider health production in a family setting similar to the one in our model, they did not address the interplay between life expectancy and the process of economic development. Browning (1994), on the other hand, considered the impact of gender-differentiated life expectancies on a couple’s savings decisions, but treated life expectancy as exogenous. Several papers are particularly relevant. Davies and Kuhn (1992) considered the intake of health related goods that endogenously affect longevity. They showed that social security programs encourage suboptimal health investment, resulting in excessive longevity. Philipson and Becker (1998) considered life expectancy under the influence of public programs, such as health care, and mortality contingent claims programs, such as social insurance. William et al. (1999) focused on the demand for health care services and its behavioral effects under competing risks with mortality endogenous. However, these papers ignored economic development and gender issues. This paper differs from the previous ones by considering gender-specific factors in the determination of life expectancy together with related decisions taken by households. Our goal is to explain changes in the gender-specific life expectancies and the gap between them in the course of economic development. Our analysis will draw on and link two important trends in recent decades in the US: first, a substantial increase in the full-time earnings of women and female labor participation in traditional male occupations; second, a declining gender gap in life expectancy since the late 1970s. While Blau and Kahn (2000) investigated evidence and causes of a narrowing gender pay gap in the US, we consider its consequences on the life expectancies of both men and women. Our paper therefore relates closely to Galor and Weil (1996) which employs a neoclassical growth model with gender-differentiated endowments to explain a narrowing gender gap in wages and declining fertility in the United States. Our model extends the basic structure in Galor and Weil (1996) by including health investment in life extension as in Grossman (1972) and Ehrlich and Chuma (1990). Our analysis resembles a traditional labor supply model as in Ehrenberg and Smith (2003) but focuses on the trade-off between time for health production and time for work, as well as the trade-off between goods for consumption and goods for health investment. By explicitly dealing with the issue of gender, we are able to investigate life expectancies by sex and the gap between them. We postulate that although women are made financially better off by the narrowing gender gap in pay, this achievement results in a lower rate of longevity growth relative to men. This paper shows that as the economy develops and income grows, though both men and women become wealthier, women may ultimately benefit less than men in terms of health. The rest of the paper is organized as follows. Section 2 describes the model. Section 3 considers the behavior of households. Section 4 confronts our model with the US data through simulation, and Section 5 concludes.

In this paper we have studied the influence of economic factors on human longevity. Unlike other studies on life extension, we consider the gender issue explicitly in the context of a neoclassical growth model. Using this approach, we have addressed several interesting questions. We show that the earnings disadvantage suffered by women in the early development of an economy is matched by an advantage over men in health status. As the economy prospers, a narrowing gender pay gap will reduce the health advantage of women. In this process, there will be increases in both time and goods investments in health by men whereas there may be a substitution of goods for time investment in health by women. The former occurs when the income effect on labor supply is stronger for men while the latter occurs when the substitution effect on labor supply is stronger for women. Also, declining fertility rates allow women to spend more time on work and health. Although women live longer than men consistently as an economy develops, the gender gap in life expectancy will eventually narrow as the wages of men and women converge. All these results are independent of the biological difference between men and women. Our analysis offers an explanation of the gender gap in life expectancy in the US. In particular, our simulation results match the observed trends of life expectancies of men and women from the 1940s to 1990s in the US. According to our model, the expanding gender gap in life expectancy before the 1970s can mainly be explained by the combination of a large gender gap in wages that induced men to increase their time investment in labor, thus being left with little time for health investment, and a rapidly declining fertility rate which gave women additional time to invest in health. On the other hand, the contracting gap in life expectancy after the 1970s can mainly be explained by a smaller gender wage gap that induced women to increase their time investment in labor, while men increased their investment in health due to the rise in household income. Moreover, as income grows in the simulation, so do the health expenditure and the life expectancy of both men and women. Although we have focused on the situation in the United States, the analysis can be applied to other countries with different patterns of life expectancy. With an appropriate specification of fertility and gender wage gaps, the model has the potential to explain gender-specific patterns of life expectancy around the world and to enrich our understanding of the economics of life expectancy.