Year	% of total
1989	99
1990	99
1991	98.1
1992	98.9
1993	98.6
1994	98.3
1995	99.6
1996	98.1
1997	97.6
1998	98
1999	98.7
2000	98.3
2001	98.5
2002	98.9
2003	99.4
2004	99.4
2005	99.4
2006	99.8
2007	99.5
2008	99.3
2009	99.4
2010	99.4
2011	99.9
2012	100
2013	100
2014	100
2015	99.4
2016	99.9
2017	99.9
2018	99.9