Year	Percent
1970	0.858
1971	0.91309
1972	0.91704
1973	0.90776
1974	0.89175
1975	0.90693
1976	0.89464
1977	0.89106
1978	0.89858
1980	0.92684
1981	0.91906
1991	0.93044
1999	0.95281
2000	1.00724
2001	0.96603
2002	0.97786
2003	0.95152
2004	0.94793
2010	0.98422
2015	1.00731