Year	% of total
1990	94
1991	93.7
1992	84.1
1993	83.6
1994	90.4
1995	89.3
1996	93.1
1997	93.8
1999	96.8
2000	96.6
2001	97.3
2002	96.7
2003	95.9
2004	97.3
2005	97.5
2006	97.8
2007	98.4
2008	99.1
2009	99.3
2010	99.6
2011	99.7
2012	99.8
2013	99.9
2014	99.9
2015	99.9
2016	99.9