Year	Percent
1970	69.58175
1971	70.01862
1972	70.4918
1973	71.07143
1974	71.5035
1975	71.91781
1976	72.43697
1977	72.86184
1978	73.3871
1979	73.89241
1980	74.53416
1981	74.88584
1982	75.37313
1983	75.84187
1984	76.54676
1985	76.9774
1986	77.53121
1987	77.95918
1988	78.47594
1989	78.97503
1990	79.58656
1991	80.07614
1992	80.64919
1993	81.20393
1994	81.64251
1995	82.283
1996	82.78689
1997	83.391
1998	83.97727
1999	84.54647
2000	85.00551
2001	85.54348
2002	86.06645
2003	86.58923
2004	87.08333
2005	87.66701
2006	88.04458
2007	88.6
2008	89.05325
2009	89.48393
2010	89.91354
2011	90.41746
2012	90.82397
2013	91.21184
2014	91.6819
2015	92.05776