Year	Percent
1969	2.8
1970	2.4
1971	1.5
1972	1.3
1973	1.2
1974	1.3
1975	2
1976	2
1977	1.8
1978	2.1
1979	2
1980	1.9
1981	2.06
1982	3.35
1983	4.11
1984	3.8
1985	3.6
1986	3.12
1987	3.79
1988	3.55
1989	3.14
1990	3.25
1991	3.42
1992	3.59
1993	4.25
1994	3.54
1995	4.35
1996	5.28
1997	5.15
1998	5.52
1999	4.7
2000	4.69
2001	4.01
2002	4.85
2003	4.78
2004	5.83
2005	5.63
2006	5.24
2007	4.86
2008	4.13
2009	5.3
2010	4.82
2011	4.56
2012	4.87
2013	5.33
2014	5.62
2015	5.72
2016	6.01
2017	5.5
2018	4.85
2019	4.49
2020	5.36