The U.S. economy contracted at an annual rate of 2.1 percent in the first quarter, according to a revised government calculation, while the Massachusetts economy shrank at a 0.3 percent rate over the same period, MassBenchmarks said Wednesday.

Revisions can significantly alter estimates of economic growth. In late April, for instance, the Commerce Department said the nation’s economy contracted at just 0.1 percent, while MassBenchmarks found a 2.6 percent growth rate for Massachusetts.

“The steep downward revision in the estimate of Massachusetts economic growth for the first quarter (originally reported as positive 2.6 percent) is primarily due to the correspondingly large downward revision in U.S. economic growth in the first quarter, originally reported as positive 0.1 percent,” Alan Clayton-Matthews, a senior MassBenchmarks editor and a Northeastern University associate professor, said in the index release.