Blacks are six times as likely as whites to be shot to death, a University of Michigan professor reports. The risk is highest, according to Reynolds Farley, a demographer with the Population Studies Center, for those between 25 and 34, when homicide is the leading cause of death. "Almost all of the rise in black homicides and much of the rise in white homicides [since the 1950s] has resulted from gun killings," he says. "There is a clear correlation between the increased availability of firearms and the increase in murders." "At present the life span for black men in the United States is about five years shorter than that of white men," says Farley, who analyzed data from the National Center for Health and other sources. "The higher homicide rate among blacks accounts for about one-fifth of that difference. Among women, homicide accounts for about one-eighth of the four-year difference in life span." Several studies have shown that homicides generally are impulsive acts and that the majority of them arise from minor disputes between spouses, lovers or friends, Farley says. "As tempers flare, one of the parties seeks a weapon. If this is a book, or a brick or a table knife, there may be an injury, but if the choice is a gun, the odds are much higher that it will result in a fatality," he says. His findings are reported in the May issue of Demography, the journal of the Population Association of America.