Year	Percent
1969	4.7
1970	5.9
1971	6.4
1972	6.3
1973	5.6
1974	5.4
1976	7.09
1977	8.05
1978	8.38
1979	7.53
1980	7.54
1981	7.61
1982	11.04
1983	12.02
1984	11.34
1985	10.5
1986	9.59
1987	8.82
1988	7.76
1989	7.55
1990	8.13
1991	10.32
1992	11.2
1993	11.38
1994	10.4
1995	9.49
1996	9.62
1997	9.1
1998	8.28
1999	7.58
2000	6.83
2001	7.22
2002	7.66
2003	7.57
2004	7.19
2005	6.76
2006	6.32
2007	6.04
2008	6.14
2009	8.34
2010	8.06
2011	7.51
2012	7.29
2013	7.07
2014	6.91
2015	6.91
2016	7
2017	6.34
2018	5.83
2019	5.66
2020	9.46