12 cities where housing bubble fears are growing

An improving economy and spiking mortgage rates are hindering people's ability to afford a house.

Data from the third quarter of 2018 showed home prices hitting their lowest level of affordability since 2008, according to Attom Data Solutions' Home Affordability Report. More than three-quarters of the 440 counties analyzed in the report posted an affordability index below their historical averages.

"Rising mortgage rates have pushed home prices to the least affordable level we've seen in 10 years, both nationally and at the local level. Close to one-third of the U.S. population now lives in counties where buying a median-priced home requires at least $100,000 in annual income," Daren Blomquist, senior vice president at Attom Data Solutions, said in a press release.

To determine affordability, the amount of income needed to make monthly house payments was calculated, assuming a 3% down payment and a 28% maximum front-end debt-to-income ratio.

Here's a look at the 12 cities with the biggest gap between the current wages needed to buy a home and the historical average. The data, from Attom, is based on counties with at least 500 home sales and where the annual income needed to buy is greater than the local average salary.

Multiple counties in the Denver-Aurora-Lakewood, Colo., and San Francisco-Oakland-Hayward, Calif., metropolitan statistical areas made the list and are combined in the rankings.