Year	Percent
1948	3.2
1949	4.9
1950	4.5
1951	3.4
1952	2.9
1953	2.2
1954	4.1
1955	3.6
1956	3.2
1957	3.4
1958	4.8
1959	4.3
1960	3.8
1961	5.1
1962	4.5
1963	4.1
1964	3.8
1965	3.3
1966	3
1967	2.8
1968	2.8
1969	2.2
1970	3.2
1971	3.5
1972	3.6
1973	3
1974	3.4
1975	5.2
1976	5.1
1977	5
1978	4
1979	3.4
1980	3.1
1981	3.2
1982	3.5
1983	3.7
1984	3.3
1985	3.2
1986	3
1987	2.5
1988	2.7
1989	2.6
1990	3
1991	3.3
1992	3.8
1993	3.2
1994	3.97
1995	3.94
1996	3.5
1997	3.21
1998	3.17
1999	3.08
2000	3.07
2001	2.95
2002	3.65
2003	3.83
2004	3.58
2005	3.48
2006	2.9
2007	3.27
2008	4.23
2009	6.44
2010	6.69
2011	6.54
2012	6.22
2013	5.35
2014	4.62
2015	3.83
2016	3.83
2017	3.59
2018	3.26
2019	2.97
2020	7.49