NEW YORK (Bloomberg) — US retail sales rose 3.9 percent last week, trailing an overall holiday forecast, as consumers delayed shopping until closer to Christmas, ShopperTrak RCT Corp. said.The 3.9 percent year-over-year sales gain for the week through December 9 follows a three percent increase for the week ended December 2. Chicago-based ShopperTrak has forecast a five percent retail sales increase from the day after Thanksgiving through January 1.

An extra shopping weekend this year has caused consumers to delay buying holiday gifts, said Bill Martin, co-founder of ShopperTrak. His words echo comments made by the International Council of Shopping Centres. Martin said sales and traffic will pick up closer to Christmas, which falls on a Monday, and Saturday, December 23, will be the busiest shopping day.

“The real bulk of the holiday shopping has yet to really come to pass,” Martin said in an interview. “When the procrastinators get to the store, we’re forecasting they’ll be spending money.”