Year	Percent
1960	2.00857
1961	2.03176
1962	2.0615
1963	2.10759
1964	2.17488
1965	2.25518
1966	2.3382
1967	2.41129
1968	2.46899
1969	2.50429
1970	2.52563
1971	2.54073
1972	2.55981
1973	2.58776
1974	2.62724
1975	2.67296
1976	2.71401
1977	2.74558
1978	2.76995
1979	2.7872
1980	2.79599
1981	2.8048
1982	2.80653
1983	2.78766
1984	2.74541
1985	2.68896
1986	2.63018
1987	2.58073
1988	2.54451
1989	2.5265
1990	2.52176
1991	2.51724
1992	2.512
1993	2.51788
1994	2.53548
1995	2.5593
1996	2.58489
1997	2.60344
1998	2.60912
1999	2.59864
2000	2.57666
2001	2.5502
2002	2.52489
2003	2.50005
2004	2.47778
2005	2.45587
2006	2.43365
2007	2.40732
2008	2.37452
2009	2.33377
2010	2.28803
2011	2.24121
2012	2.19718
2013	2.15706
2014	2.123
2015	2.09301
2016	2.06403
2017	2.03447