May 2016

Why are Inventory-Sales Ratios at U.S. Auto Dealerships so High?

Wendy E. Dunn and Daniel J. Vine


Motor vehicle dealerships in the United States tend to hold inventories equivalent to around 65 days' worth of sales, a relatively high level that has been nearly unchanged for 50 years. Despite playing a prominent role in the volatility of U.S. business cycles, very little is known about why the auto industry targets inventory stocks at such a high level. We use a panel of inventory and sales data from 41 vehicle brands over 30 years and the solutions to two well-known inventory planning problems to show that vehicle inventories appear to be related to (1) the size of dealership franchise networks, which tend to be large; (2) product variety, which tends to be high; and (3) the volatility of new vehicle sales, which also tends to be high. We show that differences across brands in these variables explain a good bit of the cross-section dispersion in brand inventory-sales ratios. Offsetting changes in these factors over time also help explain why the industry's overall inventory-sales ratio has been quite flat for many decades. More recently, the net increase observed in the inventory-sales ratio in the past couple of years is in contrast to fit of the model, which might suggest that some of that increase could reverse in the coming years.

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Keywords: Inventories, Motor Vehicles


PDF: Full Paper

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Last Update: June 19, 2020