Year	Percent
1960	1.94699
1961	1.98566
1962	2.02038
1963	2.04696
1964	2.06358
1965	2.07437
1966	2.07979
1967	2.08913
1968	2.11238
1969	2.15371
1970	2.20511
1971	2.25876
1972	2.30218
1973	2.32808
1974	2.33178
1975	2.32052
1976	2.30228
1977	2.28787
1978	2.28238
1979	2.28966
1980	2.30361
1981	2.31722
1982	2.32168
1983	2.31333
1984	2.28917
1985	2.25397
1986	2.21596
1987	2.17974
1988	2.14346
1989	2.10835
1990	2.07432
1991	2.03869
1992	2.00291
1993	1.9712
1994	1.94474
1995	1.9214
1996	1.89865
1997	1.87347
1998	1.84459
1999	1.81083
2000	1.77355
2001	1.73473
2002	1.69619
2003	1.6581
2004	1.62104
2005	1.58425
2006	1.54889
2007	1.51208
2008	1.46969
2009	1.4202
2010	1.3668
2011	1.31188
2012	1.26121
2013	1.21942
2014	1.18933
2015	1.16753
2016	1.14821
2017	1.12707