Year	Percent
1948	3.1
1949	5.2
1950	4.8
1951	3.1
1952	2.4
1953	2.7
1954	4.5
1955	4.2
1956	3.5
1957	3.4
1958	5.2
1959	4.4
1960	4.2
1961	5.4
1962	4.2
1963	4.1
1964	3.7
1965	3.1
1966	2.5
1967	2.4
1968	2
1969	1.9
1970	2.7
1971	3.3
1972	3.2
1973	2.6
1974	2.8
1975	4.6
1976	4.5
1977	3.9
1978	2.9
1979	2.9
1980	3.3
1981	3.7
1982	5.4
1983	5.6
1984	4.7
1985	4.3
1986	4.1
1987	3.5
1988	3.2
1989	3.2
1990	3.3
1991	4.1
1992	5.1
1993	4.7
1994	4.11
1995	3.59
1996	3.44
1997	2.92
1998	2.59
1999	2.68
2000	2.47
2001	3.04
2002	3.9
2003	4.12
2004	3.78
2005	3.32
2006	2.98
2007	3.09
2008	3.71
2009	6.61
2010	7.13
2011	6.64
2012	5.95
2013	5.34
2014	4.35
2015	3.78
2016	3.56
2017	3.11
2018	2.88
2019	2.57
2020	6.73