Martin noted that in 2013, Black Friday weekend produced a modest 1 percent gain, according to the firm's data, but registered a 3.1 percent gain for the season. On Tuesday, Martin said that only about 45 percent of the season's sales have taken place, noting that seven of the anticipated Top 10 sales days remain ahead.
Read MoreBlack Friday sales slip as discounts start earlier
Industry experts and retailers have openly questioned the validity of early sales data—in particular, a report from the National Retail Federation. The industry trade group, which derived its data through a poll of 4,631 consumers, said that sales over Black Friday weekend fell 11 percent.
ShopperTrak compiles its data from retailers' sales logs, though it doesn't account for online sales. It works with more than 1,000 retailers, malls and entertainment venues.