I don't know what it means or what its long-term implications might be. I only know that something profoundly serious is going on (even if hardly anyone is commenting on it) and that it will almost certainly change the character of the nation.

I have in mind the lowering of expectation. For perhaps the first time in the history of America, parents do not expect their children to be better off economically than they themselves are.

There are exceptions, of course. The school teachers whose children are in medical school or law school still expect the family fortunes to improve. The government worker whose son or daughter is pursuing a master's in business administration at a first-rate school may be thinking in upbeat terms. Low-income parents, including recent immigrants, may be hopeful with regard to their children's future.

But talk to middle-class professionals, and what you get is a near-universal sense that their children will be hard-pressed to maintain the standard of living into which they were born. Our still-at-home children may already be living in the biggest house, wearing the best clothes, enjoying the most affluent lifestyle they ever will.

Parents whose notion of natural progression involved moving from the college dorm into a one-bedroom apartment, then into a two-bedroom apartment, then to a small cottage and finally to the big house on the hill, are recognizing that, for their children, the big house on the hill may be out of the question.

Indeed, the rather modest single-family home may not be possible without two incomes and substantial help from the parents.

Part of the lowering of expectations is the result of a lowering of need, the abandonment of the hard-times-induced notion that more is better. Part of it is the result of the discovery that big homes, big cars and big bank accounts have little to do with happiness.

But the major part, I suspect, has less to do with a changing sense of values than with a changing economy. Young people may still want the things their parents worked so hard to achieve; but many find they simply cannot have them.

The adult children who come home to live with Mom and Dad do so not because they reject the idea of economic independence but because they have tried it out there and discovered that they can't hack it. As a result, parents who in other times might have pushed their children out of the nest, for fear of spoiling them, are preserving a corner of that nest against the time when their children might need it.

Nor is there much reason to suppose that this situation will soon change. The technology of computers and robotics will make our work easier, but it will also make a lot of workers unnecessary. The optimistic view is that lowering of economic ambition and the decreased need for labor will give our children time to pursue other, more humanizing, values.

But it is also a fact that our economy, at least until now, has been consumption-driven. The quintessential American notion that bigger is better and that more is a moral imperative may have had its philosophical shortcomings, but it also made the economy work.

What are the social, ethical and economic implications of lowered expectations? Will our less-ambitious children be able to take care of us in our old age, through Social Security or otherwise? What will we substitute for materialism as an engine to drive the American economy?

While it seems obvious that the answers will profoundly influence our future as a nation, we have not yet got around to considering the questions.