The answer to this question is straightforward: there is a whole lot less mobility than we like to imagine. For example, recent research (PDF) suggests that a child born into the bottom fifth of the family income distribution has a 42 percent chance of ending up there as an adult, and only a 6 percent chance of being among the top fifth of families. For children born into the top fifth, these odds are almost exactly reversed. To put this idea differently, 87 percent of children born into the bottom tenth of the income distribution will find themselves as adults in the bottom half of the distribution, while among those born into the richest tenth of families, 78 percentwill end up in the top half of the income distribution. (For a summary of the research on economic mobility, click here. For further reading about economic inequality generally, click here).

One might expect that this evidence that rags to rags and riches to riches is the normal pattern in America would lead even conservatives and libertarians to ask how we can make the playing field more level. Sadly, many responses to these disturbing facts seem to be doing everything to avoid addressing the issue of how we can give children born into poor families a better shot at prosperity.

For example, in a long Wall Street Journal opinion piece on May 18 ("The American Dream is Alive and Well"), Alan Reynolds of the Cato Institute presents such a welter of data and opinions that it is easy to miss that he hardly mentions the central point of the position he is attacking: economic mobility is very limited in the United States. Mr. Reynolds notes that it is not clear whether mobility increased or decreased from the early 1980s to the early 1990s. Besides being unsurprising—mobility is measured, after all, by comparing average incomes of parents to the incomes of their children over long periods—this discussion avoids the fact that mobility remains disturbingly low.

Mr. Reynolds then launches into a defense of inequality in income distribution. But whether or not there is too much income inequality in the United States (inequality is high compared to other advanced market economies), that has nothing to do with mobility. The question, in this discussion, is not whether the gap between the rich and the poor is something to worry about. The issue is whether the children of the poor have a decent shot at home ownership, a reliable car, and a vacation in Florida.

With the issues thoroughly obscured, Reynolds then scatters load after load of political grapeshot: the poor in America have too few earners per household (too little marriage); they don't get themselves enough education; public policy encourages them to leave school by offering the Earned Income Tax Credit; and perhaps most illogically, if poor children are immobile it is because they are in (have chosen?) bad families.

Whether Reynolds' scattered shots hit targets or not (some do, plenty do not) all of them are essentially irrelevant. The facts from study after study show that in America, the fruit does not fall far from the tree. The children of the poor are overwhelmingly likely to end up poor and the children of the rich are overwhelmingly likely to become rich. Is this the American Dream that Mr. Reynolds claims is alive and well?

If we want the American Dream to be a reality for all Americans, we will have to do better in providing children of poor parents with the opportunity to escape poverty. It's as simple as that.

Bernard Wasow is a senior fellow at The Century Foundation.