Year	Percent
1960	3.7039
1961	4.08728
1962	4.12278
1963	4.01083
1964	3.93265
1965	3.57129
1966	3.37028
1967	3.52334
1968	3.25633
1969	3.22893
1970	2.86624
1971	2.83883
1972	2.81854
1973	2.703
1974	2.65347
1975	2.84386
1976	2.68891
1977	2.95446
1978	2.74707
1979	2.84023
1980	2.7843
1981	2.86312
1982	3.14147
1983	2.84858
1984	2.86172
1985	2.76822
1986	2.72512
1987	2.71347
1988	2.61091
1989	2.5174
1990	2.36902
1991	2.24853
1992	2.213
1993	2.02783
1994	1.91306
1995	1.79424
1996	1.75661
1997	1.65927
1998	1.58065
1999	1.58983
2000	1.44663
2001	1.45355
2002	1.4457
2003	1.4613
2004	1.44139
2005	1.40998
2006	1.40622
2007	1.36773
2008	1.32173
2009	1.41416
2010	1.34154
2011	1.30325
2012	1.25035
2013	1.17993
2014	1.17465
2015	1.14357
2016	1.17306
2017	1.22507