Year	Percent
1960	2.39459
1961	2.37341
1962	2.35101
1963	2.34221
1964	2.35431
1965	2.3757
1966	2.39973
1967	2.4046
1968	2.37305
1969	2.29681
1970	2.19264
1971	2.07735
1972	1.97623
1973	1.90307
1974	1.86817
1975	1.85773
1976	1.85583
1977	1.84163
1978	1.80591
1979	1.74093
1980	1.65807
1981	1.56744
1982	1.48901
1983	1.43641
1984	1.41816
1985	1.42153
1986	1.42928
1987	1.42307
1988	1.39724
1989	1.34456
1990	1.27178
1991	1.20405
1992	1.13948
1993	1.0538
1994	0.94248
1995	0.81867
1996	0.6827
1997	0.56656
1998	0.50852
1999	0.52848
2000	0.60258
2001	0.69567
2002	0.77028
2003	0.8152
2004	0.81493
2005	0.78166
2006	0.74293
2007	0.71244
2008	0.67935
2009	0.64593
2010	0.61215
2011	0.57593
2012	0.53993
2013	0.7803
2014	0.89951
2015	0.93443
2016	1.12406
2017	1.13022