Year	Percent
1970	6.06
1971	4.8
1972	4.7
1973	4.51
1974	3.97
1975	4.55
1976	4.48
1977	3.93
1978	2.26
1979	2.12
1980	1.8
1981	1.65
1982	1.5
1983	1.69
1984	2.69
1985	4.27
1986	6.84
1987	5
1988	3.55
1989	2.35
1991	2.18
1992	3.09
1993	3.07
1994	3.03
1995	3.3
1996	3.57
1997	2.5
1998	3.41
1999	4.85
2000	3.7
2001	3.76
2002	5.65
2003	5.93
2004	5.84
2005	5.59
2006	4.48
2007	3.9
2008	3.96
2009	5.86
2010	4.12
2011	3.89
2012	3.72
2013	3.86
2014	3.74
2015	3.79
2016	4.08
2017	4.2
2019	3.1
2020	4.1