New and existing homes sold between the beginning of April and the end of June were affordable to just 62.6 percent of families earning the U.S. median income of $63,900, according to the NAHB's Housing Opportunity Index. The index declined from the 65.5 percent of homes sold that were affordable to median-income earners in the first quarter.

Housing affordability nationwide fell nearly three percent in the second quarter of 2014 as home prices increased in multiple metropolitan areas, according to the National Association of Home Builders/Wells Fargo Housing Opportunity Index (HOI), released August 14.

The national median home price increased from $195,000 in the first quarter to $214,000 in the second quarter. Meanwhile, average mortgage interest rates decreased from 4.57 percent to 4.44 percent in the same period.

"The second quarter HOI reflects the slow but steady march toward the historic levels of price appreciation and interest rates that result in affordability levels we experienced before the mid-2000s boom," said NAHB chief economist David Crowe. "While we are seeing a slight decrease in affordability, it is still fairly high by historical standards."

The NAHB report parallels recent data from the Commerce Department on the national homeownership rate, which fell in the second quarter to 64.8 percent, the lowest level since the second quarter of 1995 – a 19-year low. National homeownership declined 0.1 percent from the first quarter of 2013 and dropped 0.3 percent year-over-year.

For a seventh consecutive quarter, San Francisco-San Mateo-Redwood City, Calif. was the nation's least affordable major housing market; just 11.1 percent of homes sold in the second quarter were affordable to families earning the area's median income of $100,400.

Other major metros at the bottom of the affordability chart were Santa Ana-Anaheim-Irvine, Calif.; Los Angeles-Long Beach-Glendale, Calif.; San Jose-Sunnyvale-Santa Clara, Calif.; and New York-White Plains-Wayne, N.Y.-N.J.; in descending order.

All five least affordable small housing markets were in California. At the very bottom was Santa Cruz-Watsonville, where 16.6 percent of all new and existing homes sold were affordable to families earning the area's median income of $77,900. Other small markets included Napa, Salinas, Santa Rosa-Petaluma, and San Luis Obispo-Paso Robles, in descending order.

In contrast, Youngstown-Warren-Boardman, Ohio-Pa. claimed the title of the nation's most affordable major housing market, as 90.4 percent of all new and existing homes sold in this year's second quarter were affordable to families earning the area's median income of $52,700. Meanwhile, Cumberland, Md.-W.Va. was the most affordable smaller market, with 97.2 percent of homes sold in the second quarter being affordable to those earning the median income of $54,100.

"With interest rates near historically low levels and strengthening job growth, now continues to be a great opportunity to buy a home," said NAHB chairman Kevin Kelly.

Other major U.S. housing markets at the top of the affordability chart in the second quarter included Indianapolis-Carmel, Ind.; Syracuse, N.Y.; Harrisburg-Carlisle, Pa.; and Scranton-Wilkes-Barre, Pa; in descending order.

Meanwhile, smaller markets joining Cumberland at the top of the affordability chart included Kokomo, Ind.; Davenport-Moline-Rock Island, Iowa-Ill.; Battle Creek, Mich.; and Lima, Ohio; in descending order.

Additional HOI details, including tables and historical data, are available at nahb.org/hoi.