It’s an axiom among many Americans that each future generation will live better than its predecessor. New technologies, greater efficiencies and a can-do spirit will reward us with higher living standards. There might be periodic stumbles, but the long-term trajectory is up. And the people most guaranteed to enjoy this bountiful future are the children of today’s upper-middle class. They have all the advantages: attentive parents, good schools, a college education and job-market connections.

That’s the conventional wisdom. Ditch it.

If you are an upper-middle-class parent, as I am, you must have noticed that the real world isn’t playing according to script. Among many young Americans, there is downward mobility. The children aren’t achieving what they (and their parents) expected. Even when they have (and many have), the gains could be eroded in the future. The trajectory is not inevitably up. Parents worry about their children’s fate.

Partly, this reflects the memory of the 2007-2009 Great Recession and its huge job losses. But it’s more than that. Compared with their elders, many younger Americans are doing worse. Despite today’s strong economy, they’re falling behind.