Year	World Bank estimate
1998	32
1999	31.7
2000	31.2
2001	30.6
2002	30.3
2003	28.8
2004	26.5
2005	27.6
2006	28.3
2007	29.6
2008	27.8
2009	27.7
2010	28.6
2011	27.2
2012	26.5
2013	26.6
2014	27.2
2015	25.6
2016	25.3
2017	25.4