Year	Percent
1971	0.2949
1972	0.29824
1973	0.31966
1974	0.36497
1976	0.50698
1977	0.53245
1978	0.55905
1979	0.55254
1980	0.56185
1981	0.54101
1982	0.53701
1983	0.53247
1984	0.54921
1985	0.53391
1986	0.51762
2007	0.53675