The first category is simply cash payments, which is what many people imagine when they hear the word “compensation.” It includes wages, overtime and vacation pay, and comes to about $40 an hour. (The numbers vary a bit by company and year. That’s why $73 is sometimes $70 or $77.)

The second category is fringe benefits, like health insurance and pensions. These benefits have real value, even if they don’t show up on a weekly paycheck. At the Big Three, the benefits amount to $15 an hour or so.

Add the two together, and you get the true hourly compensation of Detroit’s unionized work force: roughly $55 an hour. It’s a little more than twice as much as the typical American worker makes, benefits included. The more relevant comparison, though, is probably to Honda’s or Toyota’s (nonunionized) workers. They make in the neighborhood of $45 an hour, and most of the gap stems from their less generous benefits.

The third category is the cost of benefits for retirees. These are essentially fixed costs that have no relation to how many vehicles the companies make. But they are a real cost, so the companies add them into the mix  dividing those costs by the total hours of the current work force, to get a figure of $15 or so  and end up at roughly $70 an hour.

The crucial point, though, is this $15 isn’t mainly a reflection of how generous the retiree benefits are. It’s a reflection of how many retirees there are. The Big Three built up a huge pool of retirees long before Honda and Toyota opened plants in this country. You’d never know this by looking at the graphic behind Wolf Blitzer on CNN last week, contrasting the “$73/hour” pay of Detroit’s workers with the “up to $48/hour” pay of workers at the Japanese companies.

These retirees make up arguably Detroit’s best case for a bailout. The Big Three and the U.A.W. had the bad luck of helping to create the middle class in a country where individual companies  as opposed to all of society  must shoulder much of the burden of paying for retirement.

So here’s a little experiment. Imagine that a Congressional bailout effectively pays for $10 an hour of the retiree benefits. That’s roughly the gap between the Big Three’s retiree costs and those of the Japanese-owned plants in this country. Imagine, also, that the U.A.W. agrees to reduce pay and benefits for current workers to $45 an hour  the same as at Honda and Toyota.