Year	Percent
1984	71.4
1987	71.4
1990	58.8
1993	58.5
1996	47.4
1998	66.6
1999	41.7
2000	39.3
2001	35.5
2002	23
2003	22.6
2004	23.9
2005	21.1
2006	27.4
2007	22.5
2008	21.4
2009	18.2
2010	15.7
2011	13.3
2012	11.7
2013	9.4
2014	7.9
2015	7.2
2016	6.5
2017	5.7