Home prices in the Hamptons slipped for the second quarter in a row, raising a question about whether a slowdown in Wall Street bonuses may be beginning to affect the luxury second-home market.

Median home prices were off 16.8% in the fourth quarter since a surge in sales in the 2011 second quarter and remain 29% below the peak prices in the spring of 2007, according to a new report by Prudential Douglas Elliman.

New York state Comptroller Thomas DiNapoli has forecast falling cash bonuses on Wall Street and a loss of 10,000 financial-sector jobs. One private compensation survey has said that bonuses are expected to shrink by an average of 20% to 30%.

Brokers and analysts said that it was too soon to tell whether the shrinking bonuses could lead to a setback to the otherwise recovering Hamptons second-home market.

“The wild card is how the decline in bonuses play out in the market,” said Jonathan Miller, an appraiser and president of Miller Samuel Inc., who prepared the market report for Prudential Douglas Elliman.

The market data showed that sales of the most expensive trophy properties on the South Fork remained stable.

But sales fell sharply for homes priced between $2.5 million and $4 million, a category that includes home buyers who can’t yet afford to live near the ocean in the most expensive enclaves “south of the highway.”

Tim Davis, a Corcoran broker who has sold some of the most expensive properties in the Hamptons, said that Wall Street bonuses are frequently part of the conversation with buyers.

Two Wall Street buyers now in contracts for houses costing less than $5 million north of Route 27 had applied for extra-large mortgages, just in case their bonuses fell short, he said. So far, he said, “There have been no complications.”

He said they were buying to take advantage of what “is very much a buyer’s market.”

The Elliman report put the median sale price in the fourth quarter at $780,000, down 8.2% from the third quarter and off 13.3% from the final quarter of 2010. The average price was $1.58 million.

The median price was driven down in part by a 16.3% increase in sales of lower-priced homes, which in the Hamptons means sales of less than $1 million, according to a separate report by Brown Harris Stevens.

Brokers say that Wall Street’s grip on the Hamptons has weakened over the years, as other buyers, entrepreneurs, real-estate developers, entertainment figures and foreign buyers have moved in over the years.

This makes it hard to distinguish between specific worries over bonuses and more general concern in the last half of 2011 over the economic fate of the U.S. and in Europe.

Andrew Saunders, founder of Saunders & Associates, a Hamptons-based real-estate firm, said the local real-estate market since the summer has closely followed the ups and downs of the economy, like “flipping a switch.”

“Whenever the news cycle tends to be a little positive, we really do see a reaction among our sidelined buyers,” he said.

Cia Comnas, who oversees Brown Harris Stevens offices in the Hamptons, said it was “premature” to conclude that bonuses were having a dampening effect on the market.

“A lot of buyers are pretty sophisticated these days,” she said. “When they start to see a well-priced product. they move on it.”