Year	Percent
1970	0.59302
1971	0.61791
1972	0.64756
1973	0.65768
1974	0.60724
1975	0.68217
1976	0.85626
1977	0.89214
1978	0.85846
1979	0.91121
1980	1.03208
1981	0.99205
1982	1.08945
1983	1.25292
1984	1.22061
1985	1.19583
1986	1.18285
1987	1.15918
1988	1.08379
1989	1.10654
1990	1.07715
1991	1.09661
1992	1.07469
1993	1.05055
1994	0.97332
1995	0.94149
1996	0.90072
1997	0.88071
1998	0.92706
1999	0.94737
2000	0.96215
2001	1.09833
2002	1.44765
2003	1.59225
2004	1.79329
2005	1.92916
2006	1.74911
2007	1.54739
2008	1.59997
2009	1.64545
2010	1.56367
2011	1.54065
2012	1.43183
2013	1.54186
2014	1.62934
2015	1.56374
2016	1.53729
2017	1.55275