Year	Percent
1971	0.57015
1972	0.57538
1973	0.58199
1974	0.58271
1975	0.60418
1976	0.62612
1977	0.64141
1985	0.76312
1988	0.78512
1990	0.81865
1991	0.84206
1992	0.85165
1993	0.86467
1994	0.87477
1995	0.88697
1997	0.91493
1999	0.93091
2000	0.93962
2001	0.94401
2002	0.94765
2003	0.94763
2004	0.96229
2005	0.96777
2006	0.972
2007	1.00026
2008	0.98602
2009	0.98381
2010	0.98616
2011	0.98562
2012	0.98329
2013	1.00852
2014	1.02689
2015	1.03498