Diana Farrell, who is now a member of America's National Economic Council but until recently worked for McKinsey, a consultancy that has spent a lot of time studying the middle classes, reckons they begin at roughly the point where people have a third of their income left for discretionary spending after providing for basic food and shelter.

ECONOMIST: Burgeoning bourgeoisie | The

In addition to those cited in this report, the author is particularly grateful for the insights, many of them off the record, of Hal Sirkin, Nandan Nilekani, Alvaro Rodriguez Arragui, Bernard Charles, Joshua Ramo, Michelle Guthrie, Arjun Divecha, Len Blavatnik, Viktor Vekselberg, Malvinder Singh, Bill Ford, Michael Green, Lord John Browne, John Studzinski, Bill Rhodes, Diana Farrell, Mikhail Fridman, Graham Mackey, Thor Bjorgolfsson, Ram Charan, Nabil Habayeb, Diana Glassman, David Rubenstein, Eli Jacobs, Dambisa Moyo, Alastair Newton and Michael Patsalos Fox.

ECONOMIST: Sources and acknowledgments

Diana and Chris Farrell said they were woken by a thud and looked out of their window to see the Metro on its side on their driveway.

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