Home prices fell in half the nation's 25 most expensive housing markets during the past year, and sales in many of those areas are down by more than 10 percent.

The latest figures from the National Association of Realtors show that home sales and prices are still very weak in most major population centers.Between the third quarters of 1989 and 1990, prices of existing homes fell in Los Angeles, San Francisco and Orange County, Calif., and in large areas of New York, New Jersey, Connecticut, Rhode Island and Massachusetts.

In all of those places, the median home price is $100,000 or more - in many cases, much more. The figures show that while home prices are falling, they're probably still too high to be affordable to many buyers.

For example, housing prices declined almost 10 percent in the Bergen-Passaic areas of New Jersey - the largest price decline in the country - but the median home price there is still $187,200. In Los Angeles, where prices are down almost 5 percent in the past year, the median home price has settled at a hefty $211,400.

Is it any wonder that home sales fell almost 19 percent in California in the past year and close to 5 percent in New Jersey?

But sales also fell in many states with more moderate prices. The Realtors said 29 states had fewer home sales in the third quarter this year than during the same period a year ago.

Sales were down 20 percent or more in Massachusetts, Delaware, Rhode Island and New Hampshire, and there were smaller double-digit decreases in California, Illinois, Tennessee, Maryland, Washington state, Arkansas, Mississippi, Nebraska and Hawaii.

There are bright spots. Texas has bounced back from a depressed market, and home sales have increased almost 9 percent in the past year.

Californians looking for affordable housing have pushed prices up almost 25 percent in the state capital, Sacramento. Some left the state and headed north to Seattle, where prices also rose by nearly 25 percent.

Philadelphia had price increases of almost 11 percent in the past year and Chicago's prices rose 9.5 percent. Prices rose in the 12 percent range in both Phoenix and Las Vegas. A number of smaller urban areas had price increases in the 3 percent to 6 percent range in the past year.

But prices were stagnant or lower in almost 50 cities.

Homebuyers sorting through these figures might note that while prices have actually fallen in 25 cities, most of the decreases so far have been nominal - 5 percent or less.

That's not enough to make much of a price difference in cities with moderately priced homes. In New Orleans, for example, a 5.5 percent price decrease reduced the median home cost from $72,900 to $68,900, a difference of only $4,000. A 4.2 percent price decrease in Dallas reduced the median price from $94,700 to $90,700, another $4,000 drop.

Such small price drops won't help many potential buyers qualify for a mortgage. With mortgage interest of 10 percent, a homebuyer would pay only $35 less each month on a mortgage of $90,700 compared with one at $94,700.

Will home prices fall further?

Prices aren't likely to rise much in the coming year if the nation sinks into a recession, as many economists are predicting. The question is whether prices and sales will rebound when the economy improves. The answer probably won't be forthcoming for another year.