Used vehicle values increased slightly in April as tracked by Black Book's Used Vehicle Retention Index that measures values of 2- to 6-year old vehicles, according to the company.

The index reached a value of 113.1 for April, which was a slight increase from March's value of 113.1. The index is calculated as a percentage of the original typically equipped retail price of a vehicle.

The month of April saw stronger-than-average vehicle value retention among car segments compared to the last few years. Traditionally strong spring season segments such as compact cars and subcompact cars have seen their overall retention strength rise during the last several weeks, according to Black Book.

The relative strength is notable because small car segments have shown significantly high depreciation for 2- to 6-year-old vehicles in the previous 12 to 24 months.

Among truck categories, compact crossovers are beginning to see accelerated depreciation over the last several weeks due to more competition within segments as well as rising supply, which has led to lower prices at auction.