America's Most Expensive Zip Codes!
Once, if a neighborhood made Forbes' list of America's 500 most expensive ZIP codes, it meant buyers were prepared to spend big bucks to call it home.

But in 2009, even in these exclusive enclaves, home prices took major hits. The ZIP codes on our list saw a 7% average drop in asking price, and in many places prices fell even more. Though Alpine, N.J. (07620), tops our list with a median asking price of $4.14 million, prices there fell 23% over the past year. Atherton, Calif. (94027), is the nation's second most expensive ZIP code, with a median asking price of $3.85 million, but prices there also declined by 23%. And New York's once-bohemian West Village neighborhood (10014) is by now fully gentrified, as demonstrated by its third-place finish and a $3.5 million median asking price. Still, over the past 12 months, prices in the West Village have fallen by 24%.

Overall, only one-fifth of America's most expensive ZIP codes saw prices rise — and in a few of those places, the data were skewed by a single high-priced listing. It’s safe to say that luxury home prices are down nearly across the board.

What's your home worth?
Take California, a state where housing speculation — and the subsequent market crash — peaked early. Last year, the Golden State accounted for 96% of America's 50 most expensive ZIP codes. This year, that figure dropped to less than 50%; 83% of those California ZIP codes that did make our list posted prices that declined or stayed the same.

But a few upscale neighborhoods are seeing prices climb again. New York's Upper West Side (10023) is one of them. Prices there have managed to inch up 4% in the past year.

"Higher-priced properties are coming on the market and staying on longer, so the stuff that is moving is lower-priced," says Michael Simonsen, CEO of Altos Research, a Mountain View, Calif.-based real-estate data firm.

The 5 most expensive ZIP codes

Alpine, N.J. (07620)
Atherton, Calif. (94027)
New York (10014)
Duarte, Calif. (91008)
Beverly Hills, Calif. (90210)
Behind the numbers
Our list comes from real-estate statistics provided by Altos Research, a national real-estate data collection and research firm that tracks over 15,000 ZIP codes, amounting to about 90% of all real-estate transactions. Home prices are based on the asking price for combined single-family and multiple-family markets. ZIPs were ranked according to the median home price.

Can anyone afford the expensive homes?

View more MSN videosGo to MSN MoneyAltos based its numbers on homes on the market as of Aug. 14, 2009, using Zone Improvement Plan codes as defined by the U.S. Postal Service. The USPS routinely adds new ZIP codes, in most cases due to shifts in population or in the volume of mail. Only a tiny percentage of new ZIPs affected our list of luxury neighborhoods, but those cases cause slightly uneven year-to-year comparisons.

Gun-shy buyers
The country's prime suburbs fared just as poorly as urban areas on our list. But unlike scores of lower-priced neighborhoods across the country, these areas are not necessarily experiencing rampant foreclosures or speculative flight. Rather, few potential buyers are biting.

Take for example affluent Atherton, where residents bring in an average annual salary of $122,571. Foreclosures don't explain its 23% price slide; only 10 homes are in foreclosure there. In picturesque Hastings-on-Hudson, N.Y. (10706), home prices have dropped 9% even though the village has no foreclosures in progress

The funny thing is that much of what I hear of California is about disasters like forest fires, and how their economy is almost bankrupt.