The Manhattan housing market, that bulletproof bellwether of residential real estate, is finally taking its lumps, according to new reports that show sales are down, listings are up, and sellers are getting frustrated.

After years of being insulated from the rest of the country’s housing woes, Manhattan properties are feeling the pinch as skittish buyers and cautious lenders are making owners wait longer to sell their co-ops and condos.

Even the luxury market – where properties generally sell faster – is taking a beating, according to an analysis of fourth-quarter sales by real-estate company Prudential Douglas Elliman.

Upper-tier homes sold between October and the end of December went for nearly 4 percent less than during the same period the year before – and stayed on the market an average of 52 days longer.

“They didn’t think Manhattan would ever get hit,” said Howard Epstein, a broker with Hercules Realty Group. “But it has.”

Prudential Douglas’ Manhattan Market Overview includes several fourth-quarter findings:

* The number of co-op sales in Manhattan fell 23.4 percent, from 1,286 units to 985 units, compared to the same period last year.

* Co-op listings increased 52.2 percent.

* Properties stayed on the market four weeks longer.

* Resale median sales prices fell 3.6 percent, from $760,000 to $732,500.

Kerry Fitzgerald, 36, an Upper West Side owner, didn’t need a market overview to know how bad things are.

She and her husband have been trying since July to sell their two-bedroom, two-bathroom West End Avenue co-op so they and their baby daughter can move to the suburbs.

Fitzgerald said they had to drop the original asking price of $1.27 million to $1.15 million. She said there had been plenty of interest, but still no takers.

“We had seven to 10 extremely interested people, and no offers ever came,” said Fitzgerald.

Corcoran Group CEO Pam Liebman said the Manhattan market started changing around the end of September.

“We weren’t affected by the subprime mortgage crisis like other states, but because of the loss of jobs, contraction of bonuses and fears of job security, the market has taken a hit,” Liebman said.

leonard.greene@nypost.com