Aug. 16, 2005 — -- Federal statistics show regular seasonal patterns for births and deaths in the United States: Births tend to peak in August and September, just as deaths hit their nadir.
Experts who have studied the trends don't agree on a cause for the fluctuating birth rate -- but most suggest factors including climate, biology and cultural traditions.
Death rates are believed to fluctuate according to the flu season. When flu is common, the elderly and ill are vulnerable, U.S. government demographers say.
Below are charts demonstrating the seasonal fluctuations in births and deaths over the period from 1995-2002.