Year	Percent
1969	4.47
1970	3.82
1971	3.46
1972	2.7
1973	2.64
1974	3.05
1976	3.47
1978	3.42
1979	2.78
1980	4.59
1981	4.92
1982	4.81
1983	4.32
1984	5.69
1985	6.33
1990	12.24
1991	13.39
1992	14.08
1993	12.74
1994	9.93
1995	8.78
1996	8.46
1997	9.75
1998	10.75
1999	11.18
2000	11.1
2001	11.81
2002	12.89
2003	13.51
2004	13.03
2005	11.34
2006	10.71
2007	9.38
2008	7.7
2009	9.53
2010	8.48
2011	7.14
2012	6.86
2013	6.21
2014	5.89
2015	5.25
2016	4.8
2017	4.22
2018	4
2019	3.8
2020	4.33