Year	Percent
1960	6.25059
1961	6.23309
1962	6.19649
1963	6.15677
1964	6.05592
1965	5.89668
1966	5.77555
1967	5.64621
1968	5.51122
1969	6.32469
1970	6.92652
1971	6.73584
1972	6.55239
1973	6.3828
1974	4.813
1975	3.64742
1976	3.64901
1977	3.64014
1978	3.63859
1979	2.83553
1980	2.18478
1981	2.09207
1982	2.06923
1983	2.14007
1984	2.36365
1985	2.71984
1986	3.19074
1987	3.4763
1988	3.53633
1989	3.3586
1990	3.00503
1991	2.57174
1992	2.24053
1993	2.05886
1994	2.03899
1995	2.16091
1996	4.14931
1997	5.1949
1998	5.20445
1999	5.15316
2000	5.07723
2001	2.89757
2002	1.75807
2003	1.80787
2004	1.88238
2005	1.99195
2006	3.16997
2007	4.03294
2008	4.04118
2009	3.96113
2010	3.84719
2011	3.70069
2012	3.59346
2013	3.49279
2014	3.43733
2015	3.40067
2016	3.35051
2017	3.27253