Cash for Clunkers: Driving Poor People Closer to the Edge

Cash for clunkers seems like a no-lose proposition. Help the environment, stimulate the economy, save jobs. This is no zero-sum game- everyone wins, right?
Well, maybe not everyone. Probabilistically speaking, what population groups are most likely to drive clunkers? Low-income people drive what they can afford, and what they can afford are often clunkers that they can buy for cash. Would they prefer to drive snappy, fuel-efficient vehicles? Mostly they would, if they could afford them. Newer cars raise the costs of driving and operating motor vehicles in ways that are especially problematic for people at the bottom of the income scale.
First, there is the issue of credit. Individuals with higher debt-to-income ratios, lower incomes, and difficult credit histories are less likely to be able to obtain financing, and will pay much higher interest rates if they are approved at all. Secondly, there is the issue of insurance. Cars financed on credit require full coverage- poor people with paid-off clunkers typically choose the minimal coverage that they can afford.
And, for low-income individuals who manage to get through this obstacle course, a final set of problems will show up when the warranty expires. Newer cars are full of bells and whistles: helpful Uncle John probably can't fix them in his garage.
So what if you can't afford to take advantage of cash for clunkers and have instead to buy a clunker to take you to your minimum-wage job? Now, the law of supply and demand becomes your problem. What happens to the clunkers that are traded in? They are crushed and sold for scrap. As the supply of clunkers diminishes, their price will rise.
The end result? More cash for those with credit good enough to take advantage of another government subsidy for the middle- and upper-classes. And, for the poor- less cash, and more expensive clunkers.