Year	2011 PPP (% of population)
1981	56.9
1984	56.9
1987	55.3
1990	55.2
1993	54.6
1996	51.7
1999	50.6
2002	47.1
2005	42.2
2008	38.3
2010	35.2
2011	32.7
2012	31.3
2013	28.8
2015	26.3