There's at least one good thing about falling home prices -- they make housing more affordable.

In the second quarter of 2009, nearly 73% of all homes sold were considered affordable for families earning the $64,000 national median income, according to the National Association of Home Builders/Wells Fargo Housing Opportunity Index (HOI).

The percentage -- 72.3 -- was down only slightly from the record 72.5% recorded in the first quarter of 2009.

The primary reason is that home prices are falling across the country. They fell an average of 20% from their 2006 peak through the end of 2008, and are expected to drop another 15% to 20% this year.

As a result, the number of homes that the median-income family can afford has steadily risen over the past couple of years, from 53.8% in the first three months of 2008, to 62.4% in the final three months of 2008, to the record high of early 2009.

In the second quarter, Indianapolis remained the most affordable major housing market. Almost 95% of all homes sold were deemed affordable to households earning the area's median family income of $68,100.

The city has been the most affordable market in the study for 16 consecutive quarters.

Other affordable major metro housing markets include Youngstown-Warren-Boardman, Ohio-Pa.; Detroit-Livonia-Dearborn, Mich.; Dayton, Ohio, and Grand Rapids-Wyoming, Mich.

The New York-White Plains-Wayne, N.Y.-N.J. region -- where only about 21% of homes sold in the period were affordable to those earning the median income of $64,800 -- was deemed the most unaffordable area.

Here's how the median sales prices in more than 140 markets have changed over the past year.