Year	Percent
1948	2.8
1949	4.7
1950	4.3
1951	2.7
1952	2.4
1953	2.3
1954	4.7
1955	3.5
1956	3.3
1957	3.4
1958	5.8
1959	4.4
1960	4.5
1961	5.4
1962	4.4
1963	4.3
1964	3.8
1965	3.2
1966	2.6
1967	2.7
1968	2.3
1969	2.3
1970	3.4
1971	4.2
1972	3.7
1973	3.2
1974	3.8
1975	6.4
1976	5.7
1977	5.1
1978	4.3
1979	4.2
1980	5.5
1981	5.8
1982	7.9
1983	8
1984	6.1
1985	5.8
1986	5.7
1987	5
1988	4.5
1989	4.2
1990	4.6
1991	5.7
1992	6.4
1993	5.8
1994	4.98
1995	4.5
1996	4.32
1997	3.93
1998	3.5
1999	3.2
2000	3.06
2001	3.77
2002	4.81
2003	5.02
2004	4.55
2005	4.14
2006	3.76
2007	3.74
2008	4.82
2009	8.29
2010	8.61
2011	7.93
2012	7.02
2013	6.31
2014	5.23
2015	4.46
2016	4.15
2017	3.75
2018	3.27
2019	3.08
2020	7.11