Year	Percent
1969	6.7
1971	5.28
1972	5.36
1973	4.77
1974	3.21
1975	3.83
1976	4.8
1977	4.47
1978	4
1979	3.5
1980	4.75
1981	5.36
1982	5.5
1983	4.89
1984	7.03
1985	6.07
1986	6.43
1987	9.1
1988	8.34
1989	8.42
1990	8.13
1991	10.6
1992	9.87
1993	9.29
1994	9.48
1995	9.53
1996	8.56
1997	8.78
1998	10.25
1999	9.81
2000	11.19
2001	3.7
2003	3.53
2004	3.55
2005	3.8
2006	4.05
2007	3.43
2008	3.72
2009	3.86
2010	3.61
2011	3.59
2012	3.5
2013	3.5
2014	3.6
2015	3.07
2016	2.7
2017	2.55
2018	2.34
2019	2.24
2020	2.52