Year	Percent
1947	3.9
1948	3.8
1949	5.9
1950	5.3
1951	3.3
1952	3
1953	2.9
1954	5.5
1955	4.4
1956	4.1
1957	4.3
1958	6.8
1959	5.5
1960	5.5
1961	6.7
1962	5.5
1963	5.7
1964	5.2
1965	4.5
1966	3.8
1967	3.8
1968	3.6
1969	3.5
1970	4.9
1971	5.9
1972	5.6
1973	4.9
1974	5.6
1975	8.5
1976	7.7
1977	7.1
1978	6.1
1979	5.8
1980	7.1
1981	7.6
1982	9.7
1983	9.6
1984	7.5
1985	7.2
1986	7
1987	6.2
1988	5.5
1989	5.3
1990	5.6
1991	6.8
1992	7.5
1993	6.9
1994	6.12
1995	5.65
1996	5.45
1997	5
1998	4.51
1999	4.22
2000	3.99
2001	4.73
2002	5.78
2003	5.99
2004	5.53
2005	5.08
2006	4.62
2007	4.62
2008	5.78
2009	9.25
2010	9.63
2011	8.95
2012	8.07
2013	7.37
2014	6.17
2015	5.28
2016	4.87
2017	4.36
2018	3.9
2019	3.67
2020	8.05