The U.S. Postal Service reports 20 billion letters, packages and cards were delivered between Thanksgiving and Christmas in 2006. The busiest mailing day last year was Dec. 18, with more than twice as many cards and letters being processed as the average on any given day.
Of that number, 12 million packages were delivered by the U.S. Postal Service throughout the 2006 holiday season through Christmas Eve. The busiest delivery day was Dec. 20.