Black Book’s Used Vehicle Retention Index finished 2018 1.9% higher than in the same time in 2017, the company announced.

This higher index shows that the used vehicle segments in the used market held their values better in 2018 than they did in 2017, on an overall basis. The 1.9% increase that Black Book observed was the highest year-over-year increase since 2012.

The firm's index reached 116.3 in December, compared to 116.5 in November. Although values were up for the year as a whole, December did experience a slight dip.

Vehicle segments that drove up the Index in December were midsize cars, midsize luxury CUV/SUVs, and compact luxury CUV/SUVs. These segments saw the biggest increases in their used value through the month.

The segments that saw the biggest declines were minivans, full-size luxury CUV/SUVs, full-size vans, midsize crossovers/SUVs, and premium sporty cars.

"The segments showing the greatest gains and declines in the Index this month were a mix of car and truck segments," said Anil Goyal, executive vice president, operations. "This is certainly the time of year when we see declines ahead of the spring selling season. However, the decline in December was higher than typical seasonality, thus a decline in the index. Given the current economic conditions, demand for used and new vehicles remains strong but there is a cloud of uncertainty as we start 2019."