Year	World Bank estimate
1985	25.2
1987	25.5
1989	26.9
2004	38
2005	35.8
2006	34.7
2007	34
2008	33.5
2009	33.4
2010	33.2
2011	33.2
2012	33
2013	33.1
2014	32.8
2015	31.8