Year	Percent
1960	2.78763
1961	2.82922
1962	2.86126
1963	2.87703
1964	2.87284
1965	2.85458
1966	2.8338
1967	2.81364
1968	2.78804
1969	2.75766
1970	2.72488
1971	2.6865
1972	2.65086
1973	2.63108
1974	2.63121
1975	2.642
1976	2.65617
1977	2.65887
1978	2.64057
1979	2.59574
1980	2.53408
1981	2.46618
1982	2.40546
1983	2.35714
1984	2.32608
1985	2.30507
1986	2.28277
1987	2.25216
1988	2.2156
1989	2.17122
1990	2.11974
1991	2.06977
1992	2.01662
1993	1.94762
1994	1.85943
1995	1.7601
1996	1.65976
1997	1.5683
1998	1.48859
1999	1.42455
2000	1.37378
2001	1.32815
2002	1.28676
2003	1.25618
2004	1.23761
2005	1.22886
2006	1.22223
2007	1.21895
2008	1.22688
2009	1.24743
2010	1.27501
2011	1.3067
2012	1.33174
2013	1.33967
2014	1.32483
2015	1.29374
2016	1.25786
2017	1.22507