Year	Percent
1971	0.44565
1973	0.45456
1974	0.44636
1975	0.4453
1977	0.43979
1985	0.47897
1986	0.48229
1987	0.48683
1999	0.61462
2000	0.63333
2001	0.64629
2002	0.66145
2003	0.67315
2004	0.69451
2011	0.80969
2013	0.83489
2014	0.84789
2015	0.85927