Year	Percent
1960	4.56779
1961	4.56856
1962	4.57586
1963	4.4297
1964	4.33829
1965	4.33531
1966	4.33466
1967	4.32374
1968	4.31264
1969	4.28001
1970	4.25373
1971	4.21493
1972	4.18262
1973	4.13932
1974	4.15074
1975	4.9067
1976	4.84315
1977	4.76993
1978	4.70646
1979	4.6414
1980	4.58184
1981	4.51373
1982	4.45424
1983	4.2154
1984	4.05482
1985	4.01607
1986	3.98531
1987	3.94444
1988	3.90473
1989	3.84784
1990	3.7952
1991	3.46669
1992	3.23576
1993	3.17762
1994	3.11682
1995	3.04704
1996	2.9816
1997	2.91399
1998	2.84057
1999	2.76008
2000	2.67496
2001	2.58523
2002	2.2152
2003	1.97391
2004	1.96461
2005	1.97577
2006	1.99385
2007	2.00713
2008	2.00507
2009	1.98532
2010	1.95483
2011	1.86827
2012	1.80166
2013	1.77375
2014	1.74585
2015	1.72197
2016	1.69421
2017	1.66669