In Atherton, Calif., 94027, the most expensive home on the market is listed for $33 million. But perhaps the best gauge of this Silicon Valley enclave’s exclusivity is the price of a starter home. The cheapest house for sale in Atherton, a 1,194-square-foot, two-bedroom bungalow on a 6,000-square-foot lot, has a $1.2 million price tag.  The median price of the 50 single-family homes that were listed for sale over the summer in Atherton 94027 is $6.67 million, making it the most expensive ZIP code in America.  “Atherton is by far the closest, most centrally located of all the super high-end communities in Silicon Valley,” says Ken Deleon, a broker in Silicon Valley whose eponymous realty firm has closed $285 million in sales in the first three quarters of 2013. “Of all the high-end luxury cities [in the Valley] it is doing the best.”  Cash-flush foreign buyers from China and India have been moving in, joining the wealthy Americans who live there. Six FORBES 400 billionaires reside in Atherton, including Google Chairman Eric Schmidt, discount brokerage tycoon Charles Schwab, and HP chief Meg Whitman. “Just two days ago I was showing a $30 million home in Atherton to a local tech CEO of a publicly traded company,” adds Deleon.  The top 10 of our list of Most Expensive ZIP Codes is dominated this year by California’s Bay Area. Atherton is followed in second place by Los Altos Hills, 94022 (not to be confused with neighboring Los Altos); Belvedere, 94920, at No. 4; and Portola Valley, 94028, at No. 9. Another seven Bay Area ZIPs round out the top 50, including Hillsborough’s 94010 (No. 13), Woodside’s 94062 (No. 22) and Palo Alto’s 94301 (No. 38).  “The California markets are more sensitive on the upside as well as the downside. It’s been a bullish housing market and the tight-inventory California markets rise faster than rest of the country as a whole,” says Michael Simonsen, chief executive of Altos Research. “It’s like a high-beta stock.”  A good analogy for a region whose economy has been super-charged by a wave of new multimillionaires and billionaires minted by the recent tech boom. The three cities of Menlo Park, Mountain View and Palo Alto, where the likes of Google, Tesla, Facebook and LinkedIn are headquartered, boast companies that have chalked up roughly $300 billion in new market capitalization since 2009. Some of that money has found its way into the local housing markets, with a growing pool of buyers bidding for a dwindling collection of homes for sale. In Los Altos Hills for example, a mere 11 homes are listed for sale and the average number of days properties spend on the market is 85.  “There’s so much money being created here by the local companies that there’s a huge amount of high-end tech buyers paying all cash,” says Deleon. “This is the strongest market we have seen here since 2000 and it feels more sustainable than 2000.”  We compiled our annual list of America’s Most Expensive Zip Codes with the help of Altos Research, a Mountain View, Calif.-based company that tracks real-time housing data. It pulled pricing information for more than 22,000 ZIP codes across the U.S. for July through September, drilling down to the 500 most expensive. Altos calculated the median asking price for single-family homes and condominiums, weighting the price based on the mix of local property types. We did not include co-ops (which may have pushed some of the fancier ZIP codes near Central Park in Manhattan lower on our list).  Altos limited the search to ZIP codes where 10 or more residences were listed for sale, including short sales and bank-owned foreclosures on the market. Homes bundled into REO bulk sales were excluded. To smooth out any wrinkles caused by a week’s unusual activity (like, say, an expensive home coming to market in an area where luxury properties are rare), Altos used a rolling average for the 90-day period.  Since our list is based on asking prices rather than closed sales or tax assessments, it may not be completely representative of the communities featured — for example, neighborhoods that have become swanky in the past few decades could contain pockets of longtime residents in more modest homes. Rather, our list is a snapshot of each market’s current activity.  “This is a view of everything actively for sale in these markets,” explains Simonsen. “It’s the experience you’ll have if you want to buy — or sell — a home today in any of them.”  Also worth noting, in some cases a ZIP may appear more than once on our list if it’s shared by two or more towns. For example, Los Altos Hills (No. 2) and Los Altos (No. 34) share 94022.  The biggest takeaway of this year’s list is the fact that inventory remains extremely tight. “Across all price points demand is high and supply is low,” says Simonsen. “Inventory is low and it looks to remain low into next year.”
The billionaire-heavy Bay Area towns of Atherton and Los Altos Hills boast the nation's highest housing prices, while the New York area has the most ZIPs on our annual list.