BARGAIN-HUNGRY Americans will need to go on a post-Christmas spending binge to salvage this holiday shopping season.

Despite the huge discounts and other incentives that stores offered leading up to Christmas, U.S. holiday sales so far this year have been the weakest since 2008, when the nation was in a deep recession.

So, stores now are depending on the days after Christmas to make up lost ground: The final week of December can account for about 15 percent of the month's sales, and the day after Christmas is typically one of the biggest shopping days of the year.

Stores, which don't typically talk about their plans for sales and other promotions during the season, are known for offering discounts of up to 70 percent in the days after Christmas. This year, they're hoping to lure more bargain hunters who held off on shopping because they wanted to get the best deals of the season.

The Macy's location in Herald Square in New York was bustling with shoppers on Wednesday. There were a variety of deals throughout the store: candy dispensers for 70 percent off, various men's clothing items for "buy one get one free," belts for 50 percent off, a bin of ties for $9.99.

Holiday sales are a crucial indicator of the economy's strength. November and December account for up to 40 percent of annual revenue for many retailers.

So far, sales of electronics, clothing, jewelry and home goods in the two months before Christmas increased 0.7 percent compared with last year, according to the MasterCard Advisors SpendingPulse report. That was the weakest holiday performance since 2008 when sales dropped sharply.

Kathy Grannis, a spokeswoman at The National Retail Federation, the nation's largest retail-trade group, said Wednesday that the trade group is sticking to its forecast for sales in the November and December period to be up 4.1 percent to $586.1 billion this year. That's more than a percentage point lower than the growth in each of the past two years, and the smallest increase since 2009 when sales were up just 0.3 percent.

Grannis noted that the trade group's definition of holiday sales also includes food and building supplies. "Stores have a big week ahead, and it's still too early to know how the holiday season fared, at this point," she said.

Spending by consumers accounts for 70 percent of overall economic activity, so the eight-week period encompassed by the SpendingPulse data is seen as a critical time not just for retailers but for manufacturers, wholesalers and companies at every other point along the supply chain.

The SpendingPulse data released Tuesday, which captures sales from Oct. 28 through Dec. 24 across all payment methods, is the first major snapshot of holiday retail sales. A clearer picture will emerge next week as retailers like Macy's and Target report revenue from stores open for at least a year. That sales measure is widely watched in the retail industry because it excludes revenue from stores that recently opened or closed, which can be volatile.

Shopping picked up in the second half of November, but then the threat of the country falling off a "fiscal cliff" gained strength, throwing consumers off track once again.

Shopping over the past two months was weakest in areas affected by Sandy and a more recent winter storm in the Midwest. Sales declined by 3.9 percent in the mid-Atlantic and 1.4 percent in the Northeast compared with last year. They rose 0.9 percent in the north central part of the country.

The West and South posted gains of between 2 percent and 3 percent, still weaker than the 3 percent to 4 percent increases expected by many retail analysts.

Online sales, typically a bright spot, grew only 8.4 percent from Oct. 28 through Saturday, according to SpendingPulse. That's a dramatic slowdown from the online sales growth of 15 to 17 percent seen in the prior 18-month period, according to the data service.

Online sales did enjoy a modest boost after the recent snowstorm that hit the Midwest, McNamara said. Online sales make up about 10 percent of total holiday business.