Year	Percent
1960	3.37394
1961	3.3511
1962	3.31976
1963	3.27827
1964	3.22685
1965	3.16888
1966	3.10741
1967	3.04544
1968	2.98324
1969	2.92225
1970	2.86218
1971	2.80283
1972	2.74364
1973	2.68432
1974	2.6248
1975	2.56591
1976	2.50789
1977	2.45307
1978	2.40354
1979	2.36055
1980	2.32201
1981	2.28588
1982	2.24971
1983	2.21321
1984	2.17596
1985	2.13839
1986	2.09969
1987	2.06236
1988	2.02952
1989	2.00234
1990	1.97819
1991	1.95709
1992	1.93229
1993	1.89547
1994	1.84309
1995	1.78166
1996	1.71709
1997	1.65955
1998	1.61491
1999	1.58728
2000	1.5715
2001	1.55862
2002	1.54211
2003	1.52222
2004	1.49679
2005	1.46746
2006	1.43775
2007	1.4094
2008	1.38101
2009	1.35269
2010	1.32442
2011	1.29597
2012	1.26703
2013	1.23651
2014	1.20412
2015	1.17082
2016	1.13706
2017	1.10394