The Commerce Department on Friday provided its first statistical snapshot of the American economy in the first quarter, the gross domestic product estimate.

The Numbers

The economy barely grew, expanding at an annual rate of only 0.7 percent.

• The growth was a sharp decline from the 2.1 percent annual rate recorded in the final quarter of last year. It was the weakest quarterly showing in three years.

The Takeaway

The first-quarter performance upset expectations for a Trump bump at the start of 2017.

The economy’s weakness reflected new caution among consumers. Other sectors like housing and business investment turned in a stronger showing, but not enough to offset factors like weaker retail sales.

Most experts believe the economy is picking up speed now, with Wall Street looking for growth at an annual rate of 2.8 percent in the second quarter. But initial hopes have been repeatedly proven too rosy lately — just two months ago, economists predicted that first-quarter growth would be roughly 2 percent.

The Background

Friday’s estimate, which will be revised twice in the coming months as more information comes in, underscores a growing debate over what data best captures economic activity.

Indicators referred to as “soft data” — surveys of corporate investment plans as well as consumer and business sentiment — have all risen since President Trump’s victory in November. And just this week, the president’s blueprint for big tax cuts for business and individuals helped fuel a renewed rally on Wall Street.

But actual economic activity — retail sales, inventory accumulation, automobile purchases — has not caught up with rising expectations, at least not yet.

Indeed, if the weakness persists, it could provide ammunition to the White House and Republicans on Capitol Hill who favor big tax cuts, since that could stimulate growth in the short term, at the risk of much higher deficits.

“Reconciling improved consumer confidence with modest levels of consumption is an exercise that will occupy us for the rest of the year,” said Carl R. Tannenbaum, chief economist at Northern Trust in Chicago, in an interview before the G.D.P. estimate’s release.

“I know there will be a school of thought that blames it on residual seasonality,” he said, referring to the winter doldrums that also reduced growth in the first three months of 2016, 2014, 2011 and 2010. “But I have to be honest: The hard data just wasn’t very good last quarter.”

“The retail retreat, especially in autos, was greater than many people anticipated,” he said.

Why would the first quarter appear weaker than expected year after year, when the government adjusts for seasonal factors like a rise in retail sales before Christmas, or a slowdown in construction in January and February?

One partial explanation is that warm winters have reduced energy spending and generation at utilities. Another is that government statisticians were having trouble compensating for sets of data that are more volatile than others, like government spending and imports and exports.

“These indicators tend to be lumpy, but they are never lumpy in the same way, so it’s tough to predict,” Mr. Tannenbaum said.