Year	Percent
1960	2.95184
1961	2.974
1962	2.99063
1963	3.00119
1964	3.00537
1965	3.0031
1966	2.99131
1967	2.97286
1968	2.95325
1969	2.93392
1970	2.91063
1971	2.88601
1972	2.84873
1973	2.78451
1974	2.68871
1975	2.57308
1976	2.45431
1977	2.34438
1978	2.24282
1979	2.15365
1980	2.07479
1981	1.98952
1982	1.90581
1983	1.84742
1984	1.82026
1985	1.80982
1986	1.81844
1987	1.80994
1988	1.74133
1989	1.59482
1990	1.40193
1991	1.1869
1992	1.00695
1993	0.90706
1994	0.91548
1995	0.99689
1996	1.10276
1997	1.17678
1998	1.1984
1999	1.14504
2000	1.04
2001	0.92537
2002	0.83037
2003	0.74912
2004	0.69048
2005	0.649
2006	0.60754
2007	0.56272
2008	0.52756
2009	0.50381
2010	0.48764
2011	0.47696
2012	0.46368
2013	0.43987
2014	0.40086
2015	0.35138
2016	0.29947
2017	0.25235