The question then is whether the tax rebates are driving battery research. Because that's what drives the performance/cost ratio of electric vehicles more than anything else (and that's what people care about, how much does it cost and how well does it work).

People always go on about the EV1 and how the owners loved it and wanted to buy it, but they don't mean they wanted to buy it for the $100,000 plus it would have really cost. And then somehow, 15 years later, we have cheaper electric cars that have much better performance characteristics. Except it isn't a mystery, batteries got a whole lot better.

In another 5 or 10 years, batteries will be even better and we will have people ranting about how it shouldn't have taken so long for practical electric cars, never mind the stupid predictable curve of battery progress you are trying to show them.