The Slowest Selling New Cars in Naperville, IL

How We Calculate Market Day Supply

Market Day Supply (MDS) measures how long it would take to sell all available inventory at the current sales pace. We calculate it as:

Importantly, we use on-lot inventory only - vehicles physically at dealerships and available for immediate purchase. We exclude:

• In-transit vehicles (0% of market) - cars that have been built and shipped but haven't arrived at the dealer yet. These aren't available to test drive or buy today.
• Excluded listings - vehicles flagged as unavailable, sold, or otherwise not actively for sale.

We also exclude vehicles with fewer than 100 on-lot listings nationwide. This filters out ultra-low-volume models (limited editions, commercial variants, etc.) where small inventory swings would produce misleading MDS numbers.

This means our "For Sale" numbers reflect what you'd actually find on a dealer lot or available to purchase on CarEdge car search - not inflated totals from industry databases that count every car on a truck.

Why This Matters

For newly launched or redesigned models, the difference can be dramatic. A car might have 20,000 units in the industry pipeline, but only 8,000 on dealer lots. Using the larger number would make the car look like it's sitting unsold when in reality dealers can barely keep up. Our on-lot methodology gives you the most accurate picture of what's actually happening at dealerships.

Data Sources

Inventory and sales data is aggregated from dealership listings across the United States, covering new vehicles at the year/make/model level. Sales volume reflects the past 45 days. Data was last updated on August 4, 2026.