Year	2011 PPP (% of population)
1981	55.7
1984	53
1987	50.1
1990	47.3
1993	44.9
1996	40.3
2002	38.6
2005	33.7
2008	29.5
2010	24.6
2011	19.8
2012	18.2
2013	16.1