When Rob Astorino launched his campaign for governor in March, he made a bold statement: His county had cut its tax levy “more than any other county in the state.”

Within days, a group aligned with the state Democratic Committee challenged the Westchester County executive’s claim, calling it “outright false.” Onondaga County had cut its tax levy by more than 20 percent since 2010, compared to Westchester’s 2.1 percent cut, the group asserted.

So who’s correct? The answer is more difficult to pin down than you might expect.

“I’m going to ask each of you the same question: Is New York winning, or is New York losing right now?” Astorino said when announcing his run against Democratic Gov. Andrew Cuomo. “I’m going to ask you for your honest answer. And then I’m going to tell you how we got Westchester back on the winning path again, by cutting the tax levy more than any other county in the state.”

When asked to back up his claim, Astorino’s campaign provided a spreadsheet of data culled from state Comptroller Thomas DiNapoli’s website.

Westchester, the data show, went from levying $702.5 million in property taxes in 2010 — Astorino’s first year in office — to $695.1 million in 2012, the most recent year available from the comptroller’s office.

The $7.4 million cut, or 1.1 percent, was the largest among the 57 counties outside New York City, both in terms of percentage and total dollar amount.

Percentage-wise, Rockland saw the largest increase in the state, jumping 26.4 percent from $109.5 million in 2010 to $138.5 million in 2010.

But the comparison between counties in the comptroller’s data isn’t perfect, some say.

The comptroller’s office includes not only the general county property taxes levied, but also special districts — taxing entities for specific sewage systems or a police force, for example — and various items like charge-back arrangements with community colleges. And each county has a different number of special districts, if any at all, with many only applying to a specific town or region.

In fact, in an advertisement during his successful re-election bid last year, Astorino’s campaign asserted his Democratic opponent, New Rochelle Mayor Noam Bramson, raised the city’s sewer tax, though the sewer district is on the county’s books. The campaign later backtracked on the claim.

“I do think it is certainly a little bit misleading,” said Westchester County Board of Legislators Majority Leader Catherine Borgia, D-Ossining. “For example, the community college, yes, there is a financial relationship, but the community college operates as its own entity, it has its own board, it creates its own budget.”

DiNapoli’s office does not collect county tax levy information that excludes special districts, though it is “working toward compiling that data,” according to spokesman Mark Johnson.

When it comes to the general, countywide property tax levy, Onondaga County has cut far more than Westchester, a review of county budget documents shows.

From 2010 to the current year’s budget, Onondaga — home to the city of Syracuse — went from a $184 million general levy to $140.9 million, a 23.4 percent cut. Westchester, comparatively, cut about $12.3 million over the same time period, from $560.7 million to $548.4 million.

“I don’t keep tabs really on the other counties and how they’re doing, but I know that in Onondaga County, that’s one thing we’ve been very focused on,” Onondaga County Executive Joanie Mahoney, a Republican who is a Cuomo ally, said last month.

E.J. McMahon, the president of the Empire Center, a fiscally conservative think-tank based in Albany, said a true comparison among counties is difficult to make when it comes to the property-tax levy, in part because each county budgets differently.

Tom Santulli, the Chemung County executive, said comparing counties’ levies is “far from an exact science.”

“I think it’s just difficult to tell the story. That’s all,” said Santulli, a Republican. “You can’t just go to one piece of paper that makes it clear how everybody did it, and who included what and who didn’t include what and have a number that makes sense.”

Democrat and Chronicle database specialist Sean Lahman contributed to this report.