The highest bid on one three-bedroom ranch house with a pool was $671,000. In 2005, the same house sold for $809,000. Another house, just steps from Naples Bay, received a high bid of $880,000, compared with $1.35 million a year earlier. On average, the bids suggested that the houses at the auction had lost about 25 percent of their value since 2005, according to Thomas Lawler, a real estate consultant who analyzed the results.

Now, Naples is not a typical housing market. House prices nearly tripled in the first half of this decade, and speculators, who are more likely than residents to sell a house in a panic, flooded into the area in recent years. But with that said, Naples is not as unusual as you may think.

The truth is that the official numbers on house prices — the last refuge of soothing information about the real estate market on the coasts — are deeply misleading. Depending on which set you look at, you’ll see that prices have either continued to rise, albeit modestly, or have fallen slightly over the last year. But the statistics have a number of flaws, perhaps the biggest being that they are based only on homes that have actually sold. The numbers overlook all those homes that have been languishing on the market for months, getting only offers that their owners have not been willing to accept.

In reality, homes across much of Florida, California and the Northeast are worth a lot less than they were a year ago. The auction in Naples may have exaggerated the downturn in the market there, but not by much. Tom Doyle, a Naples real estate agent, estimated that a typical house there, sold in the normal way, would go for about 20 percent less than it did the previous fall.

In the Boston area, prices have fallen about 10 to 15 percent since the middle of 2005, estimated Chobee Hoy, who owns a real estate brokerage firm in Brookline. Jerome J. Manning, who runs the Massachusetts-based auction company that conducted the Naples sale, told me he thought that values had dropped about 20 percent around Boston. (The government, meanwhile, says the average price rose 1 percent from last summer to this summer. But here’s all you need to know about how well the government tracks the Boston market: the index excludes any mortgage larger than $417,000.)