[jakobnev]

The "two-thirds EV and one-third gas" approach stems from data about typical driving patterns of American drivers, as used by the Society of Automotive Engineers and the Environmental Protection Agency.

That's actually mathematically incorrect since there is a decision involved when buying a vehicle that will shape the distribution of drivers actually driving the volt, ie. people don't randomly choose their vehicles, the people who actually end up driving the volt will benefit more from it's ev-only capabilities than the average driver would.

Dumbing things down to a single number is almost always a recipe for disaster.