The ongoing VW diesel emissions scandal is already taking a toll on sales of used Volkswagen models, new data shows.

Even the cars that aren't affected by the emissions scandal are becoming more difficult to sell.

Whether they are among the models found to have "defeat device" software or not, Volkswagens have been lingering on dealer lots longer, and selling at lower average prices over the past month or so.

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That's according to research firm Autolist, which compared sales data of affected TDI models to "non-scandal" Volkswagens, and a group of competitor models from other manufacturers.

The "scandal" group included 2009 to 2015 models equipped with turbocharged 2.0-liter four-cylinder engines that were the first group proven to have emissions-test cheating software.

This group comprises 482,000 vehicles in the U.S., and does not include models with the 3.0-liter V-6 that were the subject of subsequent Environmental Protection Agency (EPA) allegations.

2015 Volkswagen Passat TDI

2015 Volkswagen Passat TDI

Autolist based its analysis on four factors: vehicle time on dealer lots, deviance from expected list price, nominal list price, and price rate of change.

It found that affected diesel cars are spending an average 123 days on dealer lots, compared to 97 days for Volkswagen models not affected by the scandal.

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But even the latter figure was higher than the 86-day average for cars from other manufacturers.

List prices for scandal-affected VWs were also down nearly 5 percent from the expected average, while prices for other VW models were down around 1 percent.

2014 Volkswagen Beetle TDI

2014 Volkswagen Beetle TDI

The affected diesel models were also found to depreciate more rapidly than normal.

Other VW models depreciated more quickly in the weeks following the late-September EPA announcement, but seem to have recovered somewhat since then.

MORE: VW Diesel Owners In Limbo Until Recall Issued, While Cars Lose Value

And over roughly one month since news of Volkswagen's emissions cheating first broke, list prices for affected cars have fallen close to $1,000, Autolist says.

Volkswagen has not said what changes will be required to bring cars into compliance with emissions standards--or discussed a timeline for implementing them--but in the meantime owners will likely have to live with the fact that their cars will continue to lose value.

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