Since U.S. gas prices began falling last year, there's been much discussion about their effect on sales of hybrids and electric cars.
The knee-jerk response of many analysts is to say that low gas prices have sent consumers fleeing from the greenest models.
With less to gain from fuel savings, most people won't consider these models, they say.
New data from AutoTrader showing a decline in hybrid and electric-car sales over a period when gas prices consistently dropped would seem to confirm that narrative.
Yet a closer look reveals a more complicated situation.
Combined hybrid and electric-car sales began to decline before the slide in gas prices, the data shows.
Green-car sales reached a "plateau" even before gas prices started dropping, AutoTrader's Mark Strand told Autoblog Green.
Despite a doubling of available hybrid and electric models since 2012, sales of the combined segments actually began to decline while average gas prices were at $3.50 per gallon, he said.
The AutoTrader data shows a drop in green-car registrations every month since May 2014.
But gas prices didn't begin tumbling until July--indicating that the slowing of sales is due to factors beyond gas prices.
It should be noted that drawing conclusions from combined hybrid and electric-car sales is somewhat perilous.
Hybrids and electric cars are different types of vehicles, and appeal to different types of buyers.
2015 Nissan Leaf
In addition, hybrids sell in much higher volumes.
Lumping the two segments together risks losing the ability to distinguish electric-car sales trends in the noise of more-numerous hybrid sales.
One thing both segments have in common, though--and a possible culprit of current slow sales--is product cadence issues.
Both the Nissan Leaf and Toyota Prius are long in the tooth, and replacements won't appear until next year at the earliest.
Older models are not only less competitive, but anticipation of new versions further reduces sales--an effect known as "Osborning."
The 2016 Chevrolet Volt is set to go on sale later this year, but in the meantime a long run out is kneecapping the current model's sales.
2016 Chevrolet Volt
It's important to remember that hybrids and electric cars are subject to the same market phenomena as other vehicle types.
A model considered outdated by the public is just as tough to sell no matter what's under the hood.
While saving fuel is usually the primary reason, there are many other factors to consider when buying a new car.
Analysis of any decline in hybrid or electric-car sales should be able to account for all of them.