American fertility, as measured by the total fertility rate, apparently has been climbing since 1988 and could approach replacement level in 1990. Three possible explanations are explored: incorrect denominators, actual fertility increase, and changing ethnic proportions of the population. Using California data as a surrogate for the nation, it is found that at least part of the gain in fertility is attributable to what is called "shifting shares." Given that minorities have higher fertility than the majority, as these groups increase their share of the population, the nation's fertility can be expected to continue climbing. Any attempt to attain zero population growth must therefore be postponed indefinitely.