Parts shortages, led by the scarcity of semiconductor chips, are hobbling vehicle inventories this year.
Supply is running more than 20 percent below year-earlier levels and 30 percent below 2019 levels, according to Cox Automotive.
The days' supply of new-vehicle inventory has fallen every week since mid-February.
Inventory levels fell to 1.3 million vehicles as of April 1 from 1.5 million at the start of the year, based on self-reported data from seven automakers compiled by the Automotive News Research & Data Center.
Overall days' supply fell from 56 to 39 days for the seven automakers that continue to report monthly inventory. Subaru had the tightest supply at 24 days, while American Honda and Volvo Car USA had the highest, 55 days' supply of vehicles on April 1.
American Honda saw the largest drop in days' supply, from 80 to 55 days. Volvo was the only automaker to report an increase, up six days.
But the supply-demand imbalance is not all bad news for automakers and their retailers. Vehicle prices are up about 7 percent from a year ago, noted Michelle Krebs, executive analyst at Autotrader.
"Sales demand is strong and getting stronger as Americans return to work, get their tax refunds and stimulus checks, while production lags due to disruptions like the global chip shortage," Krebs said. "On dealer lots, selection may be hampered so shoppers will have to compromise on things like colors and features, or simply wait until supply improves."