Year	Percent
1960	0.89202
1961	0.99328
1962	1.11227
1963	1.25899
1964	1.44687
1965	1.65146
1966	1.86896
1967	2.0552
1968	2.15245
1969	2.1391
1970	2.05618
1971	1.9488
1972	1.87551
1973	1.85795
1974	1.91472
1975	2.0243
1976	2.14004
1977	2.23525
1978	2.32379
1979	2.38956
1980	2.447
1981	2.49589
1982	2.5447
1983	2.5947
1984	2.642
1985	2.68633
1986	2.72631
1987	2.75596
1988	2.76627
1989	2.75323
1990	2.7242
1991	2.695
1992	2.66827
1993	2.63528
1994	2.59889
1995	2.56206
1996	2.53244
1997	2.5113
1998	2.49846
1999	2.49162
2000	2.49604
2001	2.4977
2002	2.51512
2003	2.57298
2004	2.67879
2005	2.81308
2006	2.92988
2007	3.0233
2008	3.12148
2009	3.22412
2010	3.31339
2011	3.40972
2012	3.45821
2013	3.38323
2014	3.16529
2015	2.86218
2016	2.53781
2017	2.26486