Year	2011 PPP (% of population)
1981	71.6
1984	70.9
1987	68.4
1990	67.9
1993	66.7
1996	62.8
1999	61.3
2002	56.8
2005	50.6
2008	45.9
2010	42
2011	39
2012	37.2
2013	34.3
2015	31.3