A research by comScore stated that online Christmas season retail sales in the U.S. rose 13 percent (on y-o-y basis) to $33.8 billion, reports say. The sales increase pertains to the period from November 1 through December 14, reports suggest. Of these days, 11 days have crossed the $1 billion spend in online purchases. In the recent four days spanning December 10-14, the said sales eclipsed $1 billion, reports say.