Year	2011 PPP (% of population)
1981	53.5
1984	46.5
1987	37.4
1990	40.7
1993	35.7
1996	27.4
1999	26.3
2002	20.8
2005	12.8
2008	9.8
2010	7.7
2011	5.7
2012	4.9
2013	2.3
2015	1.6