Last week, we looked at how Norway went from subsidizing the sale of a few electric cars to making it normal to buy an electric car, and wondered how they did it.

It took not only tax abatements and incentives for electric cars, but also longstanding, onerous Norwegian taxes on gasoline and diesel vehicles.

We wondered, from the perspective of our readers, which of those types of incentives might be most effective at promoting more EV sales in the U.S.

For our Twitter poll last week, we asked: "What kind of EV incentives are most effective?" In addition to the standard Norwegian "push" and "pull" incentives, we included more ubiquitous incentives such as carpool lane access, and broke the standard EV incentives into two different types, credits and rebates, since many observers believe a straight rebate at the point of sale might be more effective than a tax credit that can be collected later, and for which some taxpayers might not qualify.

Our readers heavily favored cash-back rebates, which can lower the price of a car when someone buys it and can also lower payments for those who need a loan. That answer garnered a full 50 percent of our votes, nearly a majority. 

It got almost twice as many votes as the second choice, tax credits, as the government offers now, which proved surprisingly popular, earning 28 percent of our votes.

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The third highest vote-getter was gas taxes on internal combustion cars, which got about half the votes that tax credits did: 14 percent. 

Perhaps our readers recognize the inherent limits in expanding carpool-lane access, as only 8 percent chose them (even though quite a few surveys have been shown them to be a primary factor in many car-buyers' decisions to plug in.)

As always, our Twitter polls are unscientific, because our respondents are self-selected, and our sample size is small. If Norway is any indication, the best approach scientifically may not be to choose any of these incentives individually, but to take advantage of them all at once.