Home prices in almost one out of every five counties in the United States were less affordable than historically normal levels in the second quarter of the year, according to an analysis by the housing data company RealtyTrac. However, prices in both Connecticut and Rhode Island were considered to be within an affordable range.

In its Home Affordability Index for the second quarter of the year, RealtyTrac used publicly recorded sales deeds and average wage data from the U.S. Bureau of Labor Statistics to assess affordability in 417 counties. This information was used to determine what percentage of the county's average wages would be needed to pay a 30-year fixed rate mortgage on a median priced home, including a 3 percent down payment, property taxes, and homeowners insurance. Affordability was considered to be "historically normal" based on data going back to the first quarter of 2005.

Seventy-four counties—18 percent of the total—had an affordability index under 100, meaning prices were less affordable than usual during the quarter. The share of counties where prices were less affordable than historic norms was up from the first quarter of 2016, when 5 percent of counties fit this description. However, it was down from 20 percent in the second quarter of 2015.

"Although nearly one in five U.S. housing markets was not affordable by historic standards in the second quarter, the good news is that affordability is improving compared to a year ago in the majority of markets thanks to a combination of slowing home price appreciation and accelerating wage growth, along with falling interest rates," said Daren Blomquist, senior vice president at RealtyTrac. "For example, in San Francisco County annual home price appreciation slowed to 2 percent in the second quarter of 2016 compared to 21 percent in the second quarter of 2015, even while annual wage growth accelerated from 5 percent to 6 percent. Affordability constraints are beginning to rein in home price appreciation even while wage growth is gaining speed in an increasing number of markets."

Fifty-five percent of the counties included in the report, 228 in total, had average wages grow at a faster pace than home price appreciation. This is the first time wage growth has grown faster than home prices in more than half of these markets since the second quarter of 2012.

Home price growth continued to proceed faster than wage increases in the remaining 45 percent of the counties. This trend was observed in the metropolitan areas for cities such as Chicago, Illinois; Houston, Texas; Phoenix, Arizona; and Los Angeles and San Diego, California.

California markets continued to have some of the most pronounced affordability constraints in the nation. In Marin County, part of the San Francisco metro area, a buyer in the second quarter needed to contribute 121.7 percent of the average weekly wage in the county in order to afford monthly payments on a median priced home there. Buyers in Santa Cruz County would have to contribute 113.5 percent of the average weekly wage in the county, while San Francisco County buyers would have to contribute 94.6 percent.

However, the least affordable market identified by RealtyTrac was Kings County, New York. In this county, which includes Brooklyn, a buyer needed to contribute 121.7 percent of the average weekly wage to afford the payments on a median priced home during the second quarter.

Clayton County, Georgia, was named as the most affordable market in the United States. Located in the Atlanta metro area, buyers in this region needed to contribute just 10.4 percent of the average weekly wage in order to buy a home.

Other counties named as having the most affordable housing included Wayne County, Michigan (where the monthly payments on a median priced home were equal to 10.9 percent of the average weekly wages), Baltimore City, Maryland (11.6 percent), Bay City, Mich. (12.3 percent), and Rock Island County, Ill. (12.4 percent).

In Connecticut, RealtyTrac determined that buyers needed to contribute between 23.6 percent and 34 percent of the average weekly wage to afford monthly payments a home. The share was lowest in Hartford County, which had a median home price of $201,000, and highest in Fairfield County, which had a median home price of $379,500. In New London County, buyers needed to contribute 28.5 percent of the average weekly wages to afford the median home price of $193,500.

In Rhode Island, buyers needed to contribute between 28.6 percent and 55 percent of the average weekly wage to afford monthly payments on a home. Homes were most affordable in Providence County, which had a median home price of $199,000, and least affordable in Washington County, which had a median home price of $316,000.

RealtyTrac says the 417 counties analyzed for the report have a combined population of almost 210 million people. Counties were only included if they had a population of at least 100,000 people as well as sufficient home price and wage data.