The decline in wholesale vehicle prices grew steeper in September, and that downturn is likely to continue through the fourth quarter, according to the latest analysis from Black Book.

On Monday, the firm released its latest Used Vehicle Retention Index, which fell 3.1% month-over-month in September and dropped 3.3% year-over-year.

Granted, the decrease was not uniform, says Laura Wehunt, Black Book’s vice president of data & analytics.

“The Index declined again in September, and the size of the decline was more noticeable than what we saw earlier in the summer,” Wehunt said in an analysis. “While the overall market was down, not every segment moved the same way.”

The only one to climb in price from August was the sporty car segment, while more notable decreases were seen in full-size pickups, minivans, midsize cars and full-size crossovers/SUVs, Wehunt said.

Showing less of a decline than the overall market were prestige luxury cars and near luxury cars, she said.

“As we move through the fourth quarter, we expect depreciation to continue, especially as seasonal pressure and manufacturer incentives weigh on used-vehicle values,” Wehunt said.

Segment disparity was also on display in the retail used-car market.

Used retail prices were up just 0.2% in September, a $40 increase, according to Carfax.

While that may seem steady, there are some basic economic drivers at play that are balancing out the market, Carfax says in analysis around its monthly index, and that could have implications for both dealers and consumers.

Especially as it pertains to electric vehicles and hybrids.

“It’s a basic rule of economics: When supply is up and demand is down, prices fall. When demand is up and supplies are short, prices rise,” Carfax editor-in-chief Patrick Olsen writes in the analysis. “We can see that at work in this month’s Carfax Used Car Index.”

For instance, used prices on hybrids and EVs fell 0.8% from August to September, while prices on car segments like sedans, hatchbacks and wagons climbed 1.1% and luxury car prices were up 0.8%.

“Now, one might think that there’s higher demand for those vehicles with these gas prices, but this is a case where the supply is outstripping demand,” Olsen said, referring to EVs and hybrids.

“There are a lot of EVs coming onto the used market off of leases, and that’s helping keep their prices lower, even as drivers are looking for better fuel economy,” he said. “On the flip side, demand for used cars (sedans, hatchbacks, wagons, etc.) and used luxury cars resulted in their average price increasing as some shoppers looked for vehicles that are more fuel-efficient than SUVs or pickup trucks.”