Year	Percent
1969	4.86
1970	4.51
1971	4.57
1972	4.59
1973	4.04
1974	4.15
1975	4.18
1976	3.81
1977	3.81
1978	3.17
1979	3.81
1980	5.2
1981	4.51
1982	4.36
1983	4.07
1984	3.8
1985	3.98
1986	3.81
1987	3.09
1988	2.52
1989	2.57
1990	2.45
1991	2.41
1992	2.51
1993	2.88
1994	2.48
1995	2.06
1996	2.05
1997	2.61
1998	6.96
1999	6.34
2000	4.06
2001	3.7
2002	3.05
2003	3.35
2004	3.42
2005	3.48
2006	3.25
2007	3.01
2008	2.96
2009	3.36
2010	3.32
2011	2.99
2012	2.81
2013	2.75
2014	3.08
2015	3.55
2016	3.65
2017	3.65
2018	3.82
2019	3.75
2020	3.93