According to a new survey released by ShopperTrak on Monday, overall sales during the November-December holiday period were up. Interestingly enough, however, in-store foot traffic was down during the same time frame, which could suggest a number of different things to retailers.

Holiday sales were up 3.5 percent compared to the two-month period in 2010, with Americans spending upward of $250 billion. While this fell short of ShopperTrak's projected 3.7 percent increase, it still bodes well for the retail industry, which had observed relaxed sales leading into November.

Thanksgiving weekend saw the biggest lift in sales – year-over-year sell-through figures were observed at a 4.4 percent increase. However, this may have negatively impacted sales through the remainder of December – many consumers had to reassess their shopping budgets.

Additionally, the fact that Hanukkah didn't fall until later in the month also hindered sales in the early part of December. Sales did make a dramatic comeback leading up to Christmas, however, and the week before the holiday, a 14.4 percent lift in spending was observed.

Conversely, in-store traffic was down 3.1 percent year-over-year. There are a number of ways retailers could choose to interpret this. For one, it could suggest more Americans are forgoing crowded shopping malls in favor of online shopping. If this is true, it highlights the importance of offering an online retail platform to consumers.

ShopperTrak offers another possible explanation for the decline in foot traffic.

"We know stores saw less foot-traffic and increases in sales during the holiday season, indicating consumers were focused and took fewer trips," Bill Martin, ShopperTrak founder, told RetailingToday. "Retailers who tracked their foot-traffic daily better understood and predicted shopper trends and made the most of every opportunity that walked through their doors with appropriate inventory and staffing adjustments."

Separate data from comScore does suggest online shopping reached new highs this holiday season. Ecommerce spending topped $35 billion for the two-month period, marking a dramatic 15 percent improvement over the same time frame last year. Black Friday marked the greatest year-over-year improvement, with spending surging 26 percent on the day.