Devra Lee Davis (Letters to the Editor, Feb. 5) chose obfuscation over facts to respond to Michael Fumento's criticism "Medical Journals Give New Meaning to 'Political Science,' " editorial page, Jan. 21) of her Journal of the American Medical Association analysis of the decline in the ratio of male to female births between 1970 and 1990. While there's no doubt that the sex ratio declined, there is no support for Ms. Davis's assertion about a connection to environmental contaminants.
Refusing to look at National Center for Health Statistics data for the years prior to 1970, Ms. Davis obscured the fact that male-female birth ratios are in constant flux. The ratio for births to all races was highest in the early 1940s, declined during the 1950s and early 1960s, then rebounded by 1970. There's nothing exceptional in the sex ratio between 1970 and 1990. he ratio in the early 1940s was higher than in 1970; the ratio in the '50s and '60s was lower than in 1990. Her explanation for beginning her analysis in 1970 is that "improvements in prenatal and obstetrical care" had resulted in an increase in the sex ratio in the U.S. and in "many countries" and that she wanted to compare U.S. and other countries' data. She doesn't respond to Mr. Fumento's valid charge that she refused to acknowledge decades of U.S. data because those data show that the sex ratio fluctuates.
Focusing on two decades of data, Ms. Davis concluded in her paper what she always does: That any health trend is the result of pollution. Yet by every measure, pollution in air, water and soil has been falling since 1970. How can pollution be the cause of decreasing sex ratios if pollution itself is decreasing? Further, as Mr. Fumento pointed out, Ms. Davis's study ignored the strongest argument against a connection between general environmental pollution and the sex ratio: the inconvenient data that show the sex ratio was increasing among blacks while it was decreasing among whites and the total population. Ms. Davis tries to brush aside the black data by saying that there are too few births in the black population to draw reliable conclusions. Yet she embraces the small declines in sex ratios in other countries to support her pollution hypothesis even though the number of births in those countries (Denmark, Sweden, Finland, Norway, and Netherlands) is smaller than in American blacks.
The Centers for Disease Control and Prevention clearly disagrees both with Ms. Davis's hypothesis and her weak excuse for ignoring the figures on black births. In a paper published in the August 1998 Fertility and Sterility, it used data about the sex ratio in blacks to conclude in the agency's typically understated manner, "Environmental exposures are unlikely to account for the observed [sex ratio] trends."
Michael Gough
Adjunct Scholar
Cato Institute
Bethesda, Md.
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