By Dee-Ann DurbinNEW YORK ( TheStreet) -- The holiday shopping season got off to a strong start on Black Friday, with retail sales up 7% over last year, according to the most recent survey. Now stores just have to keep buyers coming back without the promise of door-buster savings. Buyers spent $11.4 billion at retail stores and malls, up nearly $1 billion from last year, according to a Saturday report from ShopperTrak. It was the largest amount ever spent on the day that marks the beginning of the holiday shopping season, and the biggest year-over-year increase since 2007. Chicago-based ShopperTrak gathers data from 25,000 outlets across the U.S., including individual stores and shopping centers.