comScore (NASDAQ : SCOR), a leader in measuring the digital world, today reported holiday season retail e-commerce spending for the first 29 days of the November – December 2010 holiday season. For the holiday season-to-date, $13.55 billion has been spent online, marking a 13-percent increase versus the corresponding days last year. Cyber Monday reached $1.028 billion in online spending, up 16 percent versus year ago, representing the heaviest online spending day in history and the first to surpass the billion-dollar threshold.