Year	Percent
1973	2.38
1974	2.4
1976	2.9
1978	2.72
1979	2.27
1980	3.87
1981	4.14
1982	4.16
1983	3.77
1984	4.91
1985	5.91
1990	11.009
1991	11.337
1992	11.966
1993	11.252
1994	8.184
1995	7.327
1996	7.527
1997	8.875
1998	10.391
1999	10.896
2000	11.052
2001	11.648
2002	13.009
2003	13.247
2004	12.406
2005	11.095
2006	10.422
2007	9.011
2008	7.574
2009	9.841
2010	8.94
2011	7.302
2012	6.752
2013	6.181
2014	5.866
2015	5.125
2016	4.669
2017	4.121