Housing affordability has fallen from a year ago due to a limited number of homes for-sale mixed with high buyer demand and growing home prices, according to the National Association of REALTORS® latest reading on its affordability index.

Read moreHousing Affordability Hits 2 Extremes

Home prices continue to rise at an unhealthy pace compared to incomes. What's more, lower mortgage rates are not completely offsetting the increases in home prices, according to NAR's Economists' Outlook blog.

The median single-family home price is $230,300, up 8.6 percent from May last year. Meanwhile, May's mortgage rate averaged 3.9 percent, down 44 basis points from last year (one percentage point equals 100 basis points).

NAR's index shows that housing affordability dropped from 161.2 in May 2014 to 159.7 in May 2015. The lower mortgage rates did not completely offset the rise in home prices.

Affordability is down from one month ago in all regions. The Midwest saw the largest drop of 5.8 percent, while the West dropped only 2.6 percent.

Find out how housing affordability has fared in your market, view the National Association of REALTORS®' Housing Affordability Index at REALTOR.org.

Source: "May 2015 Housing Affordability Index," National Association of REALTORS® Economists' Outlook Blog (July 10, 2015)