Morgan Stanley Analyst Adam Jonas cited a "stretched auto consumer, falling used prices and technological obsolescence of current cars" catalysts for an unprecedented slowdown in auto sales, CNBC reported.

This comes just one year after auto sales hit a record 17.55 million cars on a seasonally adjust annualized rate. That pace has slowed in 2017.

Jonas predicts auto sales around 17.3 million for this year, down from 18.3 million. He expects 15 million sales per year in both 2019 and 2020.

An annual pace of 15 million is about equal to the rate in 2013. Jonas said maintaining that rate might require government support in the form of a car purchase incentive program.

A large part of the problem is falling used car prices, which could dip as much as 50%, Jonas wrote. Because nine out of 10 new car purchases involve some sort of trade-in or off-lease deal, falling used car values will increase pressure on the auto market.

In the same note, Jonas cut price targets by more than 10% for Adient (ADNT) - Get Report , Ford (F) - Get Report , Group 1 Automotive  (GPI) - Get Report and Lear  (LEA) - Get Report .

Retail's downturn giving you the blues? Jim Cramer has a list of retailers that are currently oversold, giving investors a leg up one of the market's most volatile sectors.