It is often said that women make up a majority of the world’s population. They do not. This mistaken belief is based on generalizing from the contemporary situation in Europe and North America, where the ratio of women to men is typically around 1.05 or 1.06, or higher. In South Asia, West Asia, and China, the ratio of women to men can be as low as 0.94, or even lower, and it varies widely elsewhere in Asia, in Africa, and in Latin America. How can we understand and explain these differences, and react to them?

1.

At birth, boys outnumber girls everywhere in the world, by much the same proportion—there are around 105 or 106 male children for every 100 female children. Just why the biology of reproduction leads to this result remains a subject of debate. But after conception, biology seems on the whole to favor women. Considerable research has shown that if men and women receive similar nutritional and medical attention and general health care, women tend to live noticeably longer than men. Women seem to be, on the whole, more resistant to disease and in general hardier than men, an advantage they enjoy not only after they are forty years old but also at the beginning of life, especially during the months immediately following birth, and even in the womb. When given the same care as males, females tend to have better survival rates than males.1

Women outnumber men substantially in Europe, the US, and Japan, where, despite the persistence of various types of bias against women (men having distinct advantages in higher education, job specialization, and promotion to senior executive positions, for example), women suffer little discrimination in basic nutrition and health care. The greater number of women in these countries is partly the result of social and environmental differences that increase mortality among men, such as a higher likelihood that men will die from violence, for example, and from diseases related to smoking. But even after these are taken into account, the longer lifetimes enjoyed by women given similar care appear to relate to the biological advantages that women have over men in resisting disease. Whether the higher frequency of male births over female births has evolutionary links to this potentially greater survival rate among women is a question of some interest in itself. Women seem to have lower death rates than men at most ages whenever they get roughly similar treatment in matters of life and death.

The fate of women is quite different in most of Asia and North Africa. In these places the failure to give women medical care similar to what men get and to provide them with comparable food and social services results in fewer women surviving than would be the case if they had equal care. In India, for example, except in the period immediately following birth, the death rate is higher for women than for men fairly consistently in all age groups until the late…