The number of building permits filed in the city for individual apartments and for entire buildings is about half of what it was for the same period last year, according to data from the U.S. Census Bureau released yesterday. Manhattan saw a 69% drop-off in the number of building permits for apartment units compared with the first quarter of 2007.

Such a dramatic decrease in permits likely signals the end of the building boom in the city. The numbers come just days after the city’s buildings commissioner, Patricia Lancaster, resigned following a spike in construction-related accidents. She has been replaced on a temporary basis by First Deputy Commissioner Robert LiMandri.

The building permit slowdown “is a big number,” the president of the Real Estate Board of New York, Steven Spinola, said. “It’s clearly going to have an effect on the city. There’s going to be less housing built.”

In the first three months of 2008, the number of permits for buildings dropped 46% to 558, while the number of permits for units also fell 46% to 3,893. At the current rate, there will be permits for just 17,000 new residential units in the city in 2008, the lowest number since 2001, according to REBNY. That would be a drastic change from 2007, when there were nearly 32,000 building permits issued for individual units in New York City — the highest number since 1972, census data shows.

In Manhattan, there were permits issued for 485 new units in the first quarter, down from 1,551 for the same period in 2007. In Queens, the number of permits dropped 62% to 705; in Brooklyn,

it dropped 39% to 1,603; and in the Bronx the figure was down 17% to 862. Staten Island was the only outlier, where the number of permits increased 25% to 238.

Experts say the slowdown is largely due to the nationwide credit crisis, which has reduced developers’ access to financing.

“Money was very easy several years ago — everyone was borrowing,” said Aaron Shmulewitz, a partner at the real estate law firm Belkin Burden Wenig & Goldman. “Loan officers do not want to get burnt now. Temporarily, there is a tightening of the faucet.”

The anticipated expiration this summer of the 421-a tax abatement program likely contributed to the decrease in permits, Mr. Spinola said. “We knew there would be fewer projects after July,” he said of the program, which offered property tax abatements to market-rate developers in some areas of the city.

Last year’s record highs may have been artificially inflated by developers who were rushing to file permits and pour their foundations before the 421-a program expired. “It’s been very common, when a program sunsets, there is a big rush of permit filings beforehand,” a senior vice president at AvalonBay Communities, Frederick Harris, said. “I think the real thing is that people filed earlier than normal, not that permits have dropped.”

It is also possible that in Manhattan, where projects are so large, the dramatic decrease in permits for individual units could be the result of just a handful of developments, experts said.

Taconic Investment Partners co-founder Charles Bendit said fewer permits are actually a positive sign: “It bodes well for the market because it’ll keep a better balance between supply and demand.”

Fewer permits will also lead to lower building costs as fewer developers compete for limited resources, and may help dampen the number of construction mishaps in the city, Mr. Spinola said.

Still, the overall signal sent by fewer building permits is that the years-long building boom in New York is likely at an end. “The combination of a slowing economy and a major pullback on tax incentives is a wet blanket,” Mr. Harris said.