LAWRENCEVILLE, Ga. — Whether a seasonal trend or a sign of things to come, Black Book recorded the largest year-to-date weekly decline in car values last week. Trucks also recorded a sizable drop in values.

Volume weighted, overall car segment values fell 0.92% last week, much higher than depreciation rate of 0.61% in the previous four week. As for the overall truck segment, values decreased by 0.63%, which was higher than the 0.55% depreciation rate recorded during the previous four weeks.

“The fourth quarter typically experiences the largest depreciation in vehicle values,” said Anil Goyal, senior vice president of automotive valuation and analytics at Black Book. “This trend is already starting to show in the first two weeks of the quarter with the largest year-to-date weekly decline in car values.”

Declining the most in the car category were sporty cars, luxury cars, and full-size cars, with their wholes values falling 1.32%, 1.24%, and 1.03%, respectively. In the truck segment, subcompact crossovers, minivans and mid-size crossovers and SUVs recorded the largest weekly decline in values, falling 1.13%, 1.03%, and 0.88%, respectively.

To illustrate the drop in wholesale values, Black Book took a look at the luxury segment’s five-year trend. The firm noted that the retention rate for the segment has remained consistent in the past few years — that’s until this year when it declined slightly by three percentage points. For 2010 model-year luxury cars, retention in September 2012 was 54%. For model-year 2014 luxury cars, retention in October dropped to 50%.