Analysts expect another good year for auto sales in 2015.
But automakers may have to lean more heavily on techniques that boost sales.
Jeff Schuster of LMC Automotive says it looks like the economy will grow this year - albeit slowly.
Economic growth supports car buying.
"But the real wild card is going to be interest rates," he says.
Interest rates are low right now, but they could tick up in the second half of the year.
Schuster says automakers may need to rely more heavily on incentives, longer car loans, and leasing to keep their numbers up.
