Chart 3.

Flu, pneumonia, and common diarrhea cause many deaths; so do cholera and malaria. Children, especially those suffering from chronic malnutrition, are most at risk. And many children are not immunized against deadly infectious diseases such as diphtheria, measles, polio, tetanus, typhoid, tuberculosis, and whooping cough. In some cultures where parents prefer sons over daughters, boys receive a larger share of the limited family resources. They get more food and better health care, including immunizations. As Chart 3 shows, child mortality rates--the number of children who die between ages 1 and 5 per 1,000 children--are much higher for girls in these countries than for boys, even though research shows that girls tend to have lower child mortality rates when conditions are equal.

Despite these persistent problems, efforts on the part of countries and communities around the world to improve their children's chances of survival (see Case Study) have contributed greatly to the overall increase in life expectancy at birth because life expectancy is an average. When babies and young children die, it brings down the average more than when adults die. And when more babies live into adulthood, the average usually goes up.

Living to Old Age

Children who live past their fifth birthday have a much greater chance of living to adulthood and old age because their bodies are stronger and better able to fight off the diseases that many younger children succumb to. In fact, the longer a person lives, the greater his or her chances of reaching older ages. For example, someone who has lived to 100 is much more likely to reach 101 than someone who has just reached 90, even though the 100 year old has a very high and increasing chance of dying in the next year.

Life-threatening events and personal habits, however, may reduce the chances of living a long, productive life. In fact, some countries succeeded in improving the infant and under-5 mortality rates between 1980 and 1998 but still saw a decline in life expectancy at birth. More and more, infectious diseases such as tuberculosis (the leading cause of deaths in low- and middle-income countries) and AIDS, and chronic diseases caused by smoking (see Box 2), excessive alcohol consumption, high-fat diets, and stress-related illnesses are stealing years from the lives of men and women around the world. In addition, women and adolescent girls risk early deaths due to complications of pregnancy and childbirth, especially in countries with limited medical resources or a lack of family planning, or where women's health needs are neglected.

Life Expectancy, the Economy, and the Environment

A primary goal for sustainable development is for people to live longer, more productive, more satisfying lives. This is impossible if they do not have the resources to ensure the health and well being of themselves and their families. Poverty has a major impact on life expectancy. When governments and families cannot afford enough quality health care, education, and nutritious food, people cannot reach their full potential, either in productivity or length and quality of life. In addition, extreme poverty increases the likelihood of war and political instability, which threatens lives--and the quality of life-- as well.

There are also close links between the environment and life expectancy since we depend on natural resources such as safe water, clean air, fertile soil, and fuel to sustain life. Lack of safe water is a major cause of illness and death in low- and middle-income countries, especially among children and the elderly. Polluted air from a variety of sources such as wood fires, industrial production, and car exhaust causes lung disease and associated illnesses. Areas with overworked or eroded soil may not be able to produce enough nutritious food to support growing populations. And lack of clean fuel for cooking, boiling water, or producing heat can seriously affect people's ability to thrive.