If the monthly housing price reports seem to spread a ghastly gloom throughout every corner of San Diego County, there’s one place where prices haven’t dropped at all – southwestern Carlsbad, ZIP code 92011.

Graphic: Change in median home price by community

According to a DataQuick Information Systems analysis, that community of 21,100 residents, south of Palomar Airport Road and west of El Camino Real, had a median home price of $950,000 – an all-time peak – in the September-November period.

The other 66 ZIP code areas surveyed in the county, based on a three-month rolling average of median single-family resale home prices, have dropped from their peaks, which occurred at different times over the last four years.

And in the county’s five regions – coastal and inland North County, central San Diego, East County and South County – the price drops ranged in size and speed. The steepest drop has been in South County, which is down 22.3 percent. Central San Diego has fallen the least, down 6.6 percent.

Cal State San Marcos economist Robert Brown said the variations are no surprise.

“The housing market in San Diego County is really many different markets that are clearly interconnected but separate,” he said.

But what explains Carlsbad 92011 and its two neighboring ZIP codes, 92008 and 92009, topping the list of communities where prices are declining the least?

Agents say coastal Carlsbad is one of the most sought-after places to buy, in slow times as well as booms. Besides its proximity to the beach, it has top schools, high-tech companies with high-paying jobs and a relatively new housing stock built in master-planned communities.

Brown said those factors stand in contrast to older parts of the county where prices have dipped substantially.

Brown arrived at that conclusion by examining DataQuick’s worst-performing neighborhood, San Diego’s 92103 ZIP code that includes Hillcrest, Mission Hills, Bankers Hill, Park West and Middletown.

There, prices peaked at $961,583 last February. By November, prices were down 41 percent to $567,500.

Area real estate agents said this is not evidence that values have collapsed in this storied collection of walkable neighborhoods but that buyers had changed their expectations. People who couldn’t afford a $1 million home simply found something more modest at a lower price.

“All other things being equal, instead of buying a large home on a quiet street in Hillcrest, you can go two homes down, potentially, and find a two-bedroom, one-bath and still have a single-family home,” Brown said. “There is so much diversity in the housing stock.”

But in Carlsbad, the housing stock tends to be uniformly new, big and similar in style and appointments.

“You’re sort of constrained there,” he said, “because to look at smaller houses takes you into a townhome, the attached market.”

The only other choice is to find a home with what Brown called an “anti-amenity,” something that has reduced the value below comparable sales. In some places lately, that devaluation has come about through foreclosed properties that banks often sell at 20 percent below market.

But in Carlsbad 92011, according to RealtyTrac, there are only about a dozen bank-owned, foreclosure properties on the market. Elsewhere, such as ZIP codes in Spring Valley and eastern Chula Vista, the number of bank-owned properties is running into the hundreds.

Neighborhood median price changes also vary for a more basic reason, Brown said. The median represents the midpoint of all prices, with half above and half below that figure. If there are relatively few transactions, a high or low sales price can pull the midpoint up or down by a large amount from month to month.

To smooth out these fluctuations, DataQuick analyst Andrew LePage calculated three-month rolling averages of median prices for single-family resale houses, starting with January-March 2004. The ZIP codes were chosen because they had at least 20 transactions in the last reporting period, September-November 2007.

One other factor could be the impact of the credit crunch that developed last summer making it more difficult for buyers to get mortgages exceeding the conforming loan limit of $417,000.