Not even the strength of a hurricane generated as large of a single-month increase in the Black Book Used Vehicle Retention Index as what editors computed for August.

Black Book reported that the index posted a significant month-over-month increase of 1.4 percent. Editors indicated the change last month marked the largest single-month increase since a 1.7-percent increase registered in May 2011. The jump also is larger than the hurricane-fueled increase of 1.2 percent registered last September.

Editors explained that what’s noteworthy for this month’s Index report is that while cars overall and most individual car segments see continued declines in market share, used midsize car sales have seen an increase in market share during 2018.

Furthermore, Black Book pointed out that helping the index increase the most were compact and midsize cars and SUVs, with increases in retention ranging from 1.3 percent to 1.6 percent over the prior month.

Editors went on to mention minivans, full-size cars and luxury cars also saw sizable increases in retention (up to a 1.9-percent increase over the prior month). But those units had less impact overall due to their smaller segment size, according to Black Book.

The Black Book Used Vehicle Retention Index is calculated using Black Book’s published wholesale average value on 2- to 6-year-old used vehicles, as a percent of original typically-equipped MSRP. It is weighted based on registration volume and adjusted for seasonality, vehicle age, mileage and condition.

“No doubt, many sedan segments in the used market are defying expectations this summer, with demand increasing due to the improving job market and more consumers seeking affordable personal transportation,” said Anil Goyal, executive vice president of operations at Black Book.

“August is usually a down market from a seasonal perspective,” Goyal continued. “With nominal used-car values going up at this time of the year, the seasonally-adjusted Black Book Retention Index registered a strong lift.”

The index dates to January 2005 when Black Book published a benchmark index value of 100.0 for the market.

During 2008, the index dropped by 14.1 percent while in 2016, the index fell by just 6.4 percent.

During 2011, the index rose strongly from 113.3 to 123.0 by the end of the year as the economy picked up steam and used-vehicle values rose higher. It continued to remain relatively stable, rising slightly until May of 2014 when it hit a peak of 128.1.

To obtain a copy of the latest Black Book Wholesale Value Index, go to this website.