The return of full-freight Social Security contributions from workers' paychecks has a lot of people worrying about an imminent slowdown in consumer spending. But at least one segment of the retail industry is doing well: convenience stores.

January retail sales in the U.S. showed almost no improvement over December levels, and Q4 2012 retail sales were up only 2.2% from Q4 2011 levels. Combined with the effects of higher gas prices, experts estimate that Q1 2013 growth could be as little as 0.7% and in any event will probably show a slowdown from Q4's growth pace.

Yet last week, a report out of market researcher NPD Group showed that customer visits to convenience stores increased 4.6% in Q4, with the average shopper visiting a convenience store more often than once-a-week -- 6.2 visits per month, in fact. Part of this appears to be repeat traffic to top off the tank, with gas station convenience stores seeing above-average 3.2% growth in visits. Other popular purchases include alcoholic beverages, cigarettes/tobacco, and fresh food.

Commenting on the trends in a press release, NPD convenience-store industry analyst David Portalatin said "the c-store channel outlook is positive for 2013."