Year	% of total
1989	92
1993	93.4
1996	90
1997	94.6
2000	95.9
2001	98.5
2002	96.9
2003	97.4
2005	96.7
2006	94.5
2007	93
2008	98.3
2009	98.3
2010	95.3
2011	99.1
2012	99.5
2013	99.7
2014	99.7
2015	99.7
2016	99.7
2017	99.7
2018	99.7