Year	Percent
1971	0.51262
1972	0.5364
1973	0.55931
1974	0.57875
1975	0.5925
1976	0.60705
1977	0.62622
1978	0.64166
1979	0.66053
1980	0.69831
1981	0.7189
1982	0.74075
1983	0.75682
1984	0.77556
1985	0.79635
1986	0.81477
1987	0.82833
1988	0.83686
1989	0.84091
1990	0.85017
1991	0.85544
1992	0.86554
1993	0.88128
1994	0.88479
1995	0.89115
1996	0.90152
1997	0.91011
1998	0.91798
1999	0.91763
2000	0.92302
2001	0.92545
2002	0.9313
2003	0.94702
2004	0.95516
2005	0.96421
2006	0.97221
2007	0.98248
2008	0.98652
2009	0.98809
2010	0.98515
2011	0.98433
2012	0.98606
2013	0.98666