Black Book unveiled its May residual forecast on Monday, illustrating the downward pressure on prices that increased supply will continue to have over the next few years. 

Black Book forecast data showed that residuals on an average 3-year-old vehicle will dip from the current three-year retention of 52.0 percent in 2016, to 47.8 percent by 2019.

Analysts recapped that retention values on a 3-year-old vehicle peaked in 2013 when vehicles were retaining approximately 54.5 percent of their original typically-equipped retail. Black Book pointed out that favorable credit availability, continued growth in demand and consistently low gas prices have provided support in keeping retention rates high in the last five years.

Analysts added that increased used supply in the marketplace, driven by the significantly large volume of sales on new cars and trucks, has played a driving role in slipping retention rates this year.

Here are the historical three-year retention rates and the projected residual forecast on an average 3-year-old vehicle according to Black Book:

2012: 53.8 percent

2013: 54.5 percent

2014: 54.3 percent

2015: 54.1 percent

2016: 52.0 percent

2017: 50.1 percent (forecast)

2018: 48.6 percent (forecast)

2019: 47.8 percent (forecast)

The historical data represents published Black Book Wholesale Average values as a percent of new typically-equipped retail. The forecast represents published Black Book Residual Values averaged across all 3-year-old models.

“Despite the industry’s continued efforts to maintain a strong pace of sales on new cars and trucks, the increased level of supply in the used market has begun to weaken prices on both cars and trucks,” said Anil Goyal, Black Book’s senior vice president of automotive valuation and analytics.

“We saw the first sign of this in 2015, when cars saw above-average depreciation on the year, and this year we will see rising depreciation for truck segments as well,” Goyal continued.