Year	2011 PPP (% of population)
1981	51.6
1984	50
1987	48.2
1990	45
1993	43.8
1996	39.6
1999	38.1
2002	35.2
2005	31
2008	27.4
2010	23.3
2011	20
2012	18.6
2013	16.9
2015	14.1