Year	Percent
1969	5.9
1970	4.84
1971	4.57
1972	4.4
1973	4.23
1974	4
1975	4.92
1976	5.2
1977	5.82
1978	6.5
1979	7.12
1980	6.97
1981	6.77
1982	6.98
1983	9.2
1984	10.5
1985	11.79
1986	5.32
1987	3.63
1989	7.92
1990	8.6
1991	5.8
1992	9.4
1993	9.87
1996	7.07
1997	7.69
1998	7.75
1999	7.99
2000	7.8
2001	7.88
2002	4.84
2003	4.15
2004	4.7
2005	4.88
2006	4.18
2007	4.04
2008	4.04
2009	3.98
2010	3.58
2011	3.48
2012	3.24
2013	3.57
2014	3.21
2015	3.27
2016	3.74
2017	3.69
2018	3.49
2019	3.38
2020	7.45