Year	% of total
1987	97.7
1993	98.3
1994	98
1995	97.5
1996	98
1997	98.4
1998	98.2
1999	98.4
2000	96
2001	99.5
2002	98.7
2003	99.7
2004	99.7
2006	96.9
2008	99.5
2011	98
2012	100
2013	100
2014	100
2015	100
2016	100
2017	100