Year	Percent
1978	0.92879
1979	0.9374
1980	0.94134
1981	0.94246
1982	0.94354
1983	0.94518
1984	0.94535
1985	0.94722
1986	0.94888
1987	0.95377
1988	0.95758
1989	0.96337
1990	0.96543
1991	0.96979
1992	0.97236
1993	0.95556
1994	0.96098
1995	0.96367
1996	0.96805
1998	0.95624
1999	0.96087
2000	0.9672
2001	0.97472
2002	0.97176
2003	0.96994
2004	0.96469
2005	0.96693
2006	0.9673
2007	0.96974
2008	0.97218
2009	0.97519
2010	0.98152
2011	0.98377
2012	0.98317
2013	0.98531
2014	0.9834
2015	0.97934
2016	0.97613