In late-20th-century music, the elusiveness of the American Dream is a recurring theme. From Stevie Wonder’s ode to a boy “born in hard time Mississippi” in 1973 to Bruce Springsteen’s anthems to the working class in factory-shuttered towns in the 1980s, frustration with people’s inability to outgrow their circumstances is rife. The timing of the peak of that genre is no coincidence: whereas nearly all American children born in 1940 could still expect to do better than their parents, only two in five could by 1984.