Emerging in the 1980s and 1990s, this term describes the socio-economic segregation of urban society with special reference to New York. During the 1977–87 boom, the top 10 percent experienced a 20 percent gain in income (almost half of all gains), while the situation of lowest percentiles declined, and the numbers of poor and homeless increased.

Essentially this metaphor focused attention on a disappearing middle (mediating) class.