Year	Percent
1970	7.5
1971	7.6
1972	7.7
1973	8.9
1974	8.1
1980	7.3
1981	6.6
1982	11.7
1984	9.94
1986	10.7
1987	9.1
1990	8.53
1991	8.95
1992	8.96
1993	8.35
1994	9.04
1995	10.02
1996	11.93
1997	11.44
1998	9.36
1999	10.47
2000	12.63
2001	15.05
2002	16.65
2003	16.66
2004	12.98
2005	12.01
2006	10.84
2007	9.4
2008	8.03
2009	7.74
2010	7.16
2011	6.31
2012	6.45
2013	6.44
2014	6.55
2015	7.49
2016	7.84
2017	7.89
2018	8.34
2019	8.88
2020	10.48