Retailers racked up a slight gain in holiday sales despite a decline in customer traffic, according to a report yesterday.

The 1.7 percent sales increase for November and December — driven by last-minute splurges that spilled into the week after Christmas — failed to offset the 6-percent drop seen a year earlier, when the Wall Street crisis spooked shoppers, according to Chicago-based ShopperTrak.

Still, the results slightly surpassed the firm’s expectations. “We see stability” in spending, firm co-founder Bill Martin said, predicting first-quarter total sales will increase from a year ago.