Year	World Bank estimate
1987	21
1989	25
1993	27.9
2004	29.9
2005	34.7
2006	28.3
2007	27.9
2008	27.5
2009	27
2010	29.4
2011	29.2
2012	30.8
2013	31.5
2014	30.9
2015	30.4