The labor market seemed to defy gravity last year, generating more than 200,000 jobs a month despite a historically low unemployment rate that made it harder for employers to find workers.

Turns out job growth wasn’t as robust as it appeared.

The Labor Department revised down total job gains from April 2018 to March 2019 by 501,000, the agency said Wednesday, the largest downward revision in a decade.

The agency’s annual benchmark revision is based on state unemployment insurance records that reflect actual payrolls while its earlier estimates are derived from surveys. The preliminary figure could be revised further early next year.