Year	Percent
1948	3.6
1949	5.9
1950	5.1
1951	2.8
1952	2.8
1953	2.8
1954	5.3
1955	4.2
1956	3.8
1957	4.1
1958	6.8
1959	5.2
1960	5.4
1961	6.4
1962	5.2
1963	5.2
1964	4.6
1965	4
1966	3.2
1967	3.1
1968	2.9
1969	2.8
1970	4.4
1971	5.3
1972	5
1973	4.2
1974	4.9
1975	7.9
1976	7.1
1977	6.3
1978	5.3
1979	5.1
1980	6.9
1981	7.4
1982	9.9
1983	9.9
1984	7.4
1985	7
1986	6.9
1987	6.2
1988	5.5
1989	5.2
1990	5.7
1991	7.2
1992	7.9
1993	7.2
1994	6.1748
1995	5.6325
1996	5.4353
1997	4.9373
1998	4.416
1999	4.1147
2000	3.8995
2001	4.7987
2002	5.9312
2003	6.271
2004	5.6415
2005	5.0723
2006	4.6193
2007	4.7262
2008	6.0995
2009	10.2935
2010	10.5211
2011	9.374
2012	8.2251
2013	7.6381
2014	6.262
2015	5.3692
2016	4.9397
2017	4.3964