Year	World Bank estimate
1991	29.2
1994	29.2
1995	29
1998	28.3
2000	28.8
2001	30.3
2002	30
2003	30.3
2004	30.4
2005	32.3
2006	31.3
2007	31.3
2008	31.2
2009	30.5
2010	30.2
2011	30.5
2013	31.1
2015	31.7