NEW YORK — Americans are expected to spend more during what’s traditionally the busiest shopping season of the year, but they’re not exactly ready to shop ’til they drop like they have been in the past two years.

The National Retail Federation, the nation’s largest retail trade group, said Tuesday that it expects sales during the winter holiday shopping period in November and December to rise 4.1 percent 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.

The projections are an important indicator for retailers that depend on the last two months of the year for up to 40 percent of their annual sales. But the estimates also offer valuable insight for economists who closely watch consumer spending, which accounts for up to 70 percent of economic activity.

The holiday shopping season is one gauge of not only the shopping habits, but also the mindset of the average American during what has turned out to be a slow and uneven economic recovery. Right now, people are feeling better about rising home prices and a rebounding stock market, but job growth is still weak and prices for everything from food to gas are higher. At the same time, there’s uncertainty about who the next president will be and some Americans worry that the U.S. debt crisis could lead to another recession.

“In all the years, this is the most challenging year doing a forecast,” said Matthew Shay, president and CEO of the National Retail Federation, based in Washington, D.C. “There are so many uncertainties.”

No one’s feeling those uncertainties more than U.S. shoppers. Darlene Johnson of Silver Spring, Md., says her outlook has improved in the last few months. The value of her 401(k) retirement plan has risen. Home sales where she lives are up again, and her neighbors are getting higher prices for their houses.

Still, Johnson, who’s been grappling with higher food and gas prices, says the economy is still not stable enough for her to splurge this holiday shopping season. And she’s worried about how the debt crisis could affect her.

Johnson says last year, she overindulged and spent about $5,000. It took until this past May to pay down her credit card debt. As a result, this year, she plans to cut her holiday spending to $1,500.

It’s Americans’ worries about the economic uncertainty that led the National Retail Federation to predict slower growth in the holiday shopping season than the increase of 5.6 percent and 5.5 percent in 2010 and 2011, respectively.

Still, the forecast is higher than the average growth of 3.5 percent for November and December over the past 10 years. And it continues a growth trend that began after holiday sales fell 4.4 percent in 2008 during the middle of the recession. (The federation for the first time is counting online sales and sales from the auto parts and accessories business. It has revised every year’s holiday figures from 2000 to reflect the change.)

The federation’s forecast also is still more optimistic than the International Council of Shopping Centers, a mall trade group that last week said it predicts a 2.9 percent increase. It’s also higher than the 3.3 percent growth estimated by ShopperTrak, a Chicago-based analyzer of retail foot traffic, last month.