Year	2011 PPP (% of population)
1979	40
1989	50.3
1991	48.3
1995	39.4
1997	39.2
1998	38.9
1999	37
2000	35.5
2001	40.5
2002	37.6
2003	36.1
2004	35
2005	34.8
2006	34
2007	30.6
2008	23.3
2009	23
2010	21.8
2011	18.5
2012	18.9
2013	18.2
2014	16.9
2015	15.4
2016	14.6
2017	14.1