According to the U.S. Bureau of the Census, the resident population of the United States, projected to 04/04/07 at 17:52 GMT (EST+5) is
301,532,773
COMPONENT SETTINGS FOR MARCH 2007
One birth every.............................................. 8 seconds
One death every............................................ 12 seconds
One international migrant (net) every............ 27 seconds
Net gain of one person every......................... 12 seconds
http://www.census.gov/population/www/popclockus.html