Hiring in health care and professional services helped lift the Long Island employment market to its best showing in three months, state data released Thursday show.

The Island had 23,200 more jobs in May, compared with May 2016, the Labor Department said. It was the largest year-over-year increase since February’s 29,500-job gain.

The private education and health services sector added the most jobs, 9,800, all in health care. That sector, with its total of 271,500 jobs, is poised to become the Island’s largest. It is surpassed only by the trade, transportation and utilities sector, with 276,500 jobs. That sector includes retail.

“At the pace that it’s growing, education and health services is on track to become the largest employment sector on Long Island,” said Shital Patel, labor market analyst in the department’s Hicksville office.

But proposed changes to the Affordable Care Act, or Obamacare, could hamper that growth if millions of people nationwide, including on Long Island, lose their health coverage as the Congressional Budget Office has estimated, said economist Gregory DeFreitas, who heads Hofstra University’s labor studies program.

“Potentially there could be problems with that if we don’t diversify more,” DeFreitas said. “Otherwise, job growth is going to sink.”

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Health-care jobs accounted for 50.4 percent of Long Island’s job growth in the 12-month period ended in May, up from about a 28 percent share a decade ago, DeFreitas said. The sector grew at an annual rate of 5.4 percent in May, compared with less than 1 percent on average in 2012 and 2013, before most of the ACA provisions took effect in 2014.

“What this suggests is that Obamacare is associated with health care job growth,” DeFreitas said.

He said hospitals and ambulatory care centers have been hiring because of Medicaid expansion under Obamacare that brings in more patients. In fact, those two subsectors led local health care job creation in May.

The professional and business services sector ranked second in employment growth for the month, with 4,700 more jobs. This sector, which includes lawyers and accountants, is one of the Island’s highest paying.

Though leisure and hospitality came in fourth, with 2,300 more jobs year over year, on a month-to-month basis the sector had an even stronger showing. It added 8,500 jobs between April and May, when the typical increase is 6,800 jobs, Patel said.

John A. Rizzo, a Stony Brook University economics professor and chief economist for the Long Island Association trade group, said the strong hiring in leisure and hospitality “bodes well for the summer tourism season.”

The private sector had 20,100 more jobs in May than a year ago. The public sector expanded by 3,100. All told, the Island had 1.358 million jobs in May, compared with 1.335 million a year earlier.

The department uses year-over-year comparisons because local data aren’t adjusted to account for seasonal fluctuations in employment.

The Island’s 1.7 percent growth in employment compared with 2 percent for New York City, 1.6 for the state and 1.5 for the nation, all on the same seasonally unadjusted basis.