The U.S. economy grew less than expected in the first quarter of 2013, according to numbers released by the U.S. Commerce Department Wednesday.

Real gross domestic product, the output of goods and services produced in the U.S., grew by 1.8 per cent in the first three months of the year, instead of the 2.4 per cent growth that the agency first reported.

"The GDP estimate released today is based on more complete source data than were available for the 'second' estimate issued last month," the department said in a news release.

The previous figure had overestimated how much consumers spent and had factored in an increase in imports and exports when, in fact, they declined, when updated data is considered.

Some believe the drag on consumer spending is the result of higher taxes imposed at the start of the year.

Consumer didn't spend as much as forecast

Even with the revised estimate, the economy grew more between January and March than in the last quarter of 2012, when real GDP increased by only 0.4 per cent.

Gross domestic purchases of goods and services also increased in the first three months of 2013 — by 1.8 per cent — while consumer spending increased 2.6 per cent — down from the previous estimate of 3.2 per cent.

Government spending continued to shrink but not as dramatically, decreasing by 8.7 per cent, compared to 14.8 per cent in the fourth quarter of 2012. National defence was hardest hit, falling by 12.0 per cent, compared to 22.1 per cent.

Corporate profits decreased by $28.0 billion in the first quarter, compared to an increase of $45.5 billion in the fourth quarter of 2012.

Exports and imports were down but not by as much as in the fourth quarter, decreasing 1.1 per cent and 0.4 per cent, respectively. In the last quarter of 2012, they had dropped 2.8 per cent and 4.2 per cent, respectively.

Markets unphased

The revised GDP figure is expected to also change the forecast for the April-June quarter, which economists had estimated at two per cent or less.

The markets seemed to shrug off the more sober estimate of economic growth, and stock futures rose Wednesday.

Dow Jones industrial futures rose 70 points to 14,760. S&P futures added 6.6 points to 1,590.70. Nasdaq futures gained 20.25 points to 2,878.50.

With files from The Associated Press