Bad weather, time off from work, and lots and lots of alcohol play a key role in what researchers and condom manufacturers say is a peak time for sexual activity.
As expected, the holiday urge surge also expresses itself as a peak in U.S. births in September, according to David Lam of the University of Michigan's Population Studies Center in Ann Arbor.
Holiday intimacies aren't just an American rite, according to Gabriele Doblhammer of the Max Planck Institute for Demographic Research in Rostock, Germany. Heavy Christmas-New Year's sex "is characteristic of all Christian cultures in which it has been evaluated," she and co-researcher Joseph Lee Rogers found.
....The centrality of holidays to the timing of conceptions in the United States is relatively new, Till Roenneberg, of the Institute for Medical Psychology at the University of Munich, said in an interview.
Until the 1930s, fluctuations in temperature, sunlight and humidity yielded much larger seasonal fluctuations in U.S. conception, he said. They still do in less developed countries.
New Year's Eve produces Trojan condoms' highest sales peak, says their spokesperson, while July Fourth, Memorial Day and Labor Day aren't too shabby either.
HuffPost Lifestyle is a daily newsletter that will make you happier and healthier — one email at a time. Learn more