Even as rates on seriously delinquent and foreclosed mortgages nationwide track at their lowest levels in a decade, loan performance continues to slip in areas dependent on oil industry employment.

Nationally, 4.6% of mortgages were in some stage of delinquency (30 days or more past due including those in foreclosure) in August, according to the CoreLogic Loan Performance Insights Report. This was unchanged from July but a 0.6 percentage point decline compared with August 2016 when it was 5.2%.

The foreclosure inventory rate was 0.6%, down from 0.9% one year prior and the lowest foreclosure inventory rate for the month of August in 11 years when it was 0.5%.

For the third month in a row, the seriously delinquent rate remained at 1.9%, the lowest since October 2007, when it was also 1.9%. In August 2016, 2.6% of all mortgages were 90 days late or greater.

Loan performance slips in oil-dependent areas

"Serious delinquency and foreclosure rates are at their lowest levels in more than a decade, signaling the final stages of recovery in the U.S. housing market," said CoreLogic President and CEO Frank Martell in a press release.

"As the construction and mortgage industries move forward, there needs to be not only a ramp up in homebuilding, but also a focus on maintaining prudent underwriting practices to avoid repeating past mistakes."

The seriously delinquent rate for Alaska increased to 1.1% in August from 1% the prior year, while it was unchanged in North Dakota at 0.9%. All other states had a year-over-year decline in foreclosure rates.

"The effect of the drop in crude oil prices since 2014 has taken a toll on mortgage loan performance in some markets," said Chief Economist Frank Nothaft. "Crude oil prices this August were less than half their level three years ago. This has led to oil-related layoffs and an increase in loan delinquency rates in states like Alaska and in oil-centric metro areas like Houston."

The number of loans 30 days or more late increased in Alaska to 3.2% from 2.8% in August 2016. Houston's total delinquency rate increased to 6.2% from 5.7%.

Hurricane Harvey made landfall in Texas on Aug. 25. At least 25% of all homes affected by the storm were likely to become delinquent within four months of the storm, according to Black Knight.