Year	Percent
1960	2.60533
1961	2.61687
1962	2.62775
1963	2.6367
1964	2.64477
1965	2.64961
1966	2.65988
1967	2.66475
1968	2.64294
1969	2.58923
1970	2.51882
1971	2.44561
1972	2.39212
1973	2.37268
1974	2.39431
1975	2.44601
1976	2.49879
1977	2.54609
1978	2.60443
1979	2.6741
1980	2.74588
1981	2.81559
1982	2.87035
1983	2.90028
1984	2.89942
1985	2.87534
1986	2.84429
1987	2.81032
1988	2.76409
1989	2.70643
1990	2.64107
1991	2.56934
1992	2.49726
1993	2.43289
1994	2.37848
1995	2.32956
1996	2.28102
1997	2.22625
1998	2.16433
1999	2.09272
2000	2.01467
2001	1.94087
2002	1.86876
2003	1.78727
2004	1.69369
2005	1.59586
2006	1.49514
2007	1.40712
2008	1.34783
2009	1.32602
2010	1.32993
2011	1.34212
2012	1.34834
2013	1.34718
2014	1.3342
2015	1.31198
2016	1.28984
2017	1.27048