There used to be a basic bargain in this country that if you worked hard and played by the rules, you could own a home, afford a car, put your kids through college and take a modest vacation every year while putting enough away for a comfortable retirement. In the second half of the 20th century, millions of Americans achieved this solid middle-class lifestyle. I should know — I grew up in that America. But things have changed. Today’s working Americans and the young are justified in having greater doubts about the future than any generation since the Depression. Americans...