"2015 was a standout year for the auto industry," said Bill Fay, Toyota division group vice president and general manager.
Edmunds.com notes that light trucks (including pickups and SUVs) have outsold cars in each of the last 28 months, with no signs of slowing down.
Edmunds projects that dealers will have sold the largest share of trucks and SUVs in December, almost 60 percent of all new-vehicle sales, more than in any other month on record.
Leases accounted for 29 percent of all new retail sales, the highest level ever.
The average new car transaction price in 2015 was $33,188, up 2.5 percent from $32,386 in 2014.
Edmunds forecasts that there will be 18.1 million new car and truck sales in 2016.
Fiat-Chrysler celebrated a strong finish to 2015, with a December sales increase of 13 percent compared with sales in December 2014.
It was the automaker's best December sales since it started in business as Chrysler more than 90 years ago.
The Dodge Journey SUV turned in its best December sales ever.
Nissan posted a 19 percent December sales increase compared to a year ago. The Nissan Rogue SUV set a December record at 26,479, for an increase of 78 percent.
Ford tallied U.S. December sales of 239,242 vehicles, up 8 percent versus a year ago.
"Strong demand for F-150 contributed to the performance, as F-Series broke through the 85,000-vehicle mark for the first time in a decade," Ford said in a statement.
Edmunds says: Car shoppers making plans for 2016 may want to keep in mind that unemployment is projected to dip to around 4 percent, which traditionally is considered to be "full employment," according to economists. In addition, despite recent interest rate hikes, auto loan rates may be subsidized by automakers to keep them lower.