Year	World Bank estimate
1981	43.6
1989	42.4
2006	45.9
2007	46.4
2008	45.1
2009	45.6
2010	44.5
2011	42.2
2012	39.9
2013	40.5
2014	40.1
2015	40.2
2016	39.7
2017	39.5