Another simple equation:

4% of the world's population
25% of the world's annual oil consumption
(from the article linked above)

Works fine for a few decades until the rest of the world decides they want their piece of the dream as well. And they have money now, so they can compete for the (limited) oil.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue