In a Black Book graph showing year-to-date used-vehicle value movements, the trend line for trucks shows more waves than the line for car segments.

But lately, both are consistently moving downward, the company said in the latest Black Book Market Insights report.

“Both car and truck segments are starting to show a consistent depreciation rate in the last four weeks, with truck depreciation picking up from the spring season,” Anil Goyal, senior vice president of automotive valuation and analytics, said in the report.

Bottom line: Trucks had the upper hand over cars in terms of value retention during the spring market. But the speed at which truck values have declined has increased in the past four weeks, Black Book said.

Car segment values fell 0.47 percent last week on a volume-weighted basis, which is consistent with 0.44-percent depreciation in the two weeks prior. Likewise, the 0.33-percent dip for trucks aligned with 0.30 percent dip from the previous two weeks.

The truck segment with the largest decline last week was the midsize luxury crossover/SUV, with a 0.78-percent drop. Among cars, the largest drop was for compacts (down 0.82 percent).

Full-size cars (up 0.06) was the only segment (car or truck) to see an increase.