Used car prices fell by 0.4% in December 2012, compared with November last year, according to What Car?'s own used car valuation figures.
Family cars represented the best bargains, dropping 0.9% in price, while coupes were the biggest climbers with an average price increase of 0.8%.
Average prices for both diesel and petrol models fell by 0.4%.
Across all sectors, the price of one-year-old models fell by 0.4% compared with December 2011, while three-year-old cars dropped in value by 0.5%. Five-year-old models fell by 0.2%.
Retained values also changed. One-year-old models were worth an average 0.3% more than the month before with a 68.6% average retained value, while three-year-old cars increased by 0.1% to 52.2%. Five-year-old cars rose 0.3% to 37.2%.
SUVs were the best performers after one year, with an average retained value of 78.5%, while family cars held on to the least at 63.8%.
After three years, SUVs retain 60.5% of their new value, the best of any sector. Luxury cars fell to the bottom of the list on an average of 44.1%.