Black Friday isn’t the best day for discounts, but Dec. 18 is, according to ShopAdvisor.

The price-tracking firm found that 42 percent of products during last year’s holiday shopping season were more expensive the day after Thanksgiving than in the four weeks leading up to it.

The pricing data came from 16,000 real-time feeds from retailers and affiliates, including the nation’s leading department store chains and online retailers. ShopAdvisor looked at the lowest available prices for 6,000 products across all major categories that its mobile app and website users shopped for last season. Prices in stores and online were lowest on Dec. 18, at an average 17.5 percent discount versus an average of less than 5 percent on Black Friday.

In 2012, prices were lowest on Dec. 1, the day after Black Friday, according to ShopAdvisor.

"What is now clear, if it wasn't already, is that Black Friday is more about sport than savings – consumers competing for real deals on just a handful of limited quantity doorbusters, not widespread season's-best pricing," said Scott Cooper, CEO of ShopAdvisor, in a statement Thursday.

ShopAdvisor also found that December discounts were 30 percent deeper on weekdays than on weekends. Discounts continued after Christmas through New Year’s Day, but the deals weren’t as strong as those offered on Dec. 18.

This week, the top five most-watched categories by ShopAdvisor’s users are TVs, tablets and computers, health and beauty, appliances, cameras and video games.