Year	Percent
1970	5.44
1971	5.44
1972	6.39
1973	6.37
1974	5.38
1975	5.82
1976	6.64
1977	7.12
1978	7.24
1979	7.64
1980	7.53
1982	9.03
1983	8.57
1984	9.41
1985	9.41
1986	10.55
1987	10.72
1988	10.97
1989	10.99
1990	9.79
1991	10.1
1992	9.33
1993	10.24
1994	11.09
1995	11.67
1996	11.87
1997	12
1998	12.12
1999	11.69
2000	10.84
2001	9.6
2002	9.21
2003	8.87
2004	7.87
2005	7.73
2006	6.78
2007	6.08
2008	6.72
2009	7.75
2010	8.36
2011	8.36
2012	10.65
2013	12.15
2014	12.68
2015	11.9
2016	11.69
2017	11.21
2018	10.61
2019	9.95
2020	9.16