Year	% of total
1986	100
1999	98.7
2000	98.6
2001	98.6
2002	98.6
2003	98.6
2004	98.2
2005	98.2
2006	98.4
2007	98.4
2008	98.5
2009	98.3
2010	96.8
2011	96.9
2012	97
2013	96.9
2014	96.9
2015	97.1
2016	96.2
2017	97.1
2018	96.2
2019	96.2