Retailers were left a bit disappointed during the 2013 holiday shopping season, initial data shows.

According to retail industry research firm ShopperTrak, U.S. consumers spent $265.9 billion at stores during November and December 2013, a mere 2.7 percent increase in sales from 2012's holiday season. The increase is just below the 3 percent growth between 2011 to 2012. 

The 2013 holiday season marks the fourth consecutive year with increased retail sales, the Chicago-based firm found.

Although sales rose, foot traffic in stores declined 14.6 percent, ShopperTrak said.

ShopperTrak found that Christmas week accounted for more than 15 percent of all shopping revenue from the holiday. Black Friday, Nov. 29, saw the highest level of sales, as well as the most foot traffic, of any day during the season. Still, Black Friday sales dropped 13 percent from 2012 due to stores staying open longer on Thanksgiving Day.

Shoppers had a shorter holiday season from Black Friday through Christmas in 2013, only 25 days with four weekends, compared to 2012, which had 31 days with five weekends. ShopperTrak says the reduced number of days and severe weather in early December meant more people shopped earlier in the season or waited for last-minute deals online.

The Los Angeles Times reported data from online retail analytics firm Custora that found e-commerce sales during the holiday season grew 12 percent compared to the period in 2012. Online shopping was this season's "shining star in a lukewarm holiday retail environment," the paper reports.

ShopperTrak founder Bill Martin said in a press release that although the holiday numbers aren't as robust as retailers would like, the 2.7 percent increase from 2012 is a sign that the economy is picking up. He said he believes 2014 will be even better, especially for those companies who have both physical stores and an online shop:

"We will continue to see the trend of steady sales increases as consumer confidence rises and the economy progresses," Martin said. "And, while foot traffic will continue to slow due to changing consumer patterns--with more shoppers purchasing online or researching products online before heading to stores--retailers must remember an overwhelming majority of all retail sales in the U.S. will occur in brick-and-mortar stores. Retailers who deliver a seamless customer experience both in the store and across all channels will emerge ahead of the rest."