Black Book’s Used Vehicle Retention Index increased from 112.6 to 113.9 in September, the largest month-over-month gain since March 2012, according to a company announcement.

This increase, Black Book noted, was in part due to the estimated 500,000 cars and trucks needing to be replaced as a result of Hurricane Harvey.

“We certainly anticipated a near-term increase in the Index in last month’s report, and with the storm replacement activity kicking in we believe this activity will continue in the next month, but not much longer,” said Anil Goyal, senior vice president of automotive valuation and analytics for Black Book.

Segment-wise, some of the strongest beneficiaries in terms of used vehicle retention were compact cars, compact crossover SUVs, full-size cars, and mid-size cars. Respectively, these segments saw their values rise 2.8%, 2.4%, 2.5% and 2.3%.

"We saw a nice bump in several car segments, and we also anticipate several truck segments to see increases as well, especially with the demand for service and construction vehicles. It was interesting that mainstream car segments and compact SUVs experienced the largest increase in immediate replacement demand,” said Goyal.

Black Book’s Used Vehicle Retention Index is calculated using Black Book’s published wholesale average value on two- to six-year-old used vehicles, as a percent of original typically-equipped MSRP. The index dates back to January 2005 when black book published the benchmark index value of 100.0 for the used auto market.