Depends on the focus. If the goal were as stated, the methodology failed to take into account that the old cars were taken off the road, regardless of whether the trades would have otherwise been made. Without the program, the old cars would still have been traded in, but would not have been removed from the streets. This assumes that the purpose of the program were actually to remove high mpg and high polluting cars from the road.
If the actual purpose were to put money into the hands of auto makers and dealers, the methodology was probably okay. Considering the stake our government has in two of the car makers, I suppose the methodology was okay.
