Year	Percent
1948	7.3
1949	10.8
1950	9.3
1951	5.7
1952	6.2
1953	5.9
1954	10.6
1955	8.7
1956	8.5
1957	9
1958	13.1
1959	11
1960	11.2
1961	13
1962	11.3
1963	12.2
1964	11.5
1965	10.1
1966	8.6
1967	8.7
1968	8.7
1969	8.4
1970	11
1971	12.7
1972	12.1
1973	10.5
1974	11.9
1975	16.1
1976	14.7
1977	13.6
1978	12.3
1979	11.8
1980	13.9
1981	14.9
1982	17.8
1983	17.2
1984	13.9
1985	13.6
1986	13.3
1987	12.2
1988	11
1989	10.9
1990	11.2
1991	13.4
1992	14.2
1993	13.4
1994	12.54
1995	12.19
1996	12.11
1997	11.44
1998	10.44
1999	9.9
2000	9.34
2001	10.56
2002	12
2003	12.43
2004	11.85
2005	11.31
2006	10.51
2007	10.54
2008	12.85
2009	17.6
2010	18.42
2011	17.31
2012	16.21
2013	15.55
2014	13.4
2015	11.62
2016	10.43
2017	9.24
2018	8.61
2019	8.39
2020	14.92