New-vehicle inventories tightened further in September to just 2.11 million vehicles, a decline of about 150,000 vehicles from the previous month, as sales return while production struggles to keep up.

The inventory composite, compiled by Cox Automotive, is the lowest industry inventory level in nine years, according to the Automotive News Data Center, and represents more than 1 million fewer new vehicles available for sale than at the same point a year earlier, Cox said.

Most automakers no longer report monthly inventory levels. However, among those that do, Toyota was the only automaker whose days’ supply didn’t grow slightly month over month.

Cox estimates the industrywide inventory level at a 55-day supply.

Model-year turnover also has been slow because of delayed factory retooling, Cox said.

Suppliers and automakers are fighting an uphill battle to bring their production back up after COVID-19 forced factories to suspend operations.

Cox said inventory shortages are most acute in the midsize-pickup segment, with a 35-day supply, while full-size pickups had a below-average 50-day supply.