Year	Percent
1960	1.54014
1961	1.57547
1962	1.87434
1963	1.83729
1964	1.97586
1965	2.12064
1966	2.05889
1967	1.80528
1968	1.56297
1969	1.66392
1970	1.85959
1971	1.33879
1972	0.69074
1973	0.55874
1974	0.67141
1975	0.65507
1976	0.45068
1977	0.44088
1978	0.37678
1979	0.30499
1980	0.28848
1981	0.13556
1982	0.0572
1983	0.04526
1984	0.09088
1985	0.16517
1986	0.23257
1987	0.33368
1988	0.4596
1989	0.66719
1990	0.77261
1991	0.80672
1992	0.77504
1993	0.7666
1994	0.89613
1995	0.70739
1996	0.26646
1997	0.09062
1998	0.08887
1999	0.11127
2000	0.1939
2001	0.32202
2002	0.39915
2003	0.44694
2004	0.46691
2005	0.47232
2006	0.69403
2007	0.92852
2008	0.96565
2009	1.03581
2010	1.03375
2011	1.03809
2012	1.11773
2013	1.21575
2014	1.35346
2015	1.41162
2016	1.60132
2017	1.78521