Mergers, acquisitions and relocations at some of Long Island’s largest public companies mean the combined revenue and head count at the region’s remaining top 25 public companies in 2016 are substantially less than in 2012, according to data from S&P Global Market Intelligence.

Combined revenue for the top 25 companies declined 24 percent from 2012 and 15.7 percent from the prior year to $31.5 billion in 2016. The decline occurred because large companies left the list, not because Long Island’s remaining public companies are shrinking in size. Combined profits of the top 25 slid 22.3 percent from 2012 to $2.3 billion in 2016, according to the S&P Global Market Intelligence report prepared for Newsday. The information is current for companies as of May 31 and is based on filings with the U.S. Securities and Exchange Commission.

Overall employee head count, including non-Long Island jobs, fell 31.3 percent during the same period to 68,821.

Companies remaining on the list grew from 2012 to 2016.

Henry Schein Inc. remained king of Long Island’s corporate hill in 2016 with revenue of $11.6 billion. That was a 29.4 percent increase from 2012 and an 8.8 percent increase from 2015.

The Melville-based distributor of products for the practices of dentists, doctors and veterinarians also ranked No. 1 in profits, at more than a half-billion dollars, and market capitalization of $14.6 billion as of May 31.

advertisement | advertise on newsday

Stanley M. Bergman, chairman and chief executive of Henry Schein, attributed the company’s rise to organic growth and acquisitions or joint ventures. The strategy combines “geographic expansion, deeper market penetration” and new product offerings, he said in a statement.

For Long Island overall, the loss of CA Technologies Inc., Pall Corp. and Cablevision Systems Corp. — three of the top five companies on the 2012 list — left a gaping hole, even though all three businesses retain operations in the region. CA moved its headquarters to Manhattan in 2014. Pall was acquired by Danaher Corp. in 2015.

Altice USA, which acquired Cablevision and owns 25 percent of Newsday, last week announced plans to move its headquarters from Bethpage to Long Island City in Queens, although it will continue to have major operations on Long Island. Altice USA, a unit of Amsterdam-based Altice N.V., also is in the process of staging an initial public offering to raise at least $1.26 billion.

Of the 60 Long Island-based public companies whose annual revenue in fiscal 2016 was at least $1 million, 25, or 41.7 percent, saw a year-over-year decline in sales.

Long Island’s 25 top public companies in 2016 notched a 3.7 percent year-over-year revenue increase compared with 2015. That compares with a 2.9 percent revenue decline for the top 100 New York City companies.

Though the region has lost some of its marquee public companies, John Rizzo, chief economist at the Long Island Association, said that the economy remains buoyant.

The unemployment rate fell from 7.4 percent in 2012 to 4.1 percent in 2016, he said. “The overall picture for companies on Long Island improved substantially during this period.”

Insulating the Island’s economy from exits by large public companies is the abundance of small businesses. More than 95 percent of enterprises on Long Island are considered small businesses, employing fewer than 500 workers, Rizzo said.

Rizzo also said the ability of Long Island companies, such as medical device makers, to keep sophisticated manufacturing and high-end jobs in the region will require a workforce with refined technical skills.

“That kind of manufacturing has a future rather than wrapping Hershey’s Kisses,” he said.