Year	Percent
1970	79.86726
1971	80.47722
1972	81.10403
1973	81.3278
1974	81.91057
1975	82.47012
1976	82.846
1977	83.3652
1978	83.70787
1979	84.22018
1980	84.86486
1981	85.33569
1982	85.78856
1983	86.22449
1984	86.64441
1985	87.07038
1986	87.62058
1987	87.99368
1988	88.50932
1989	89.00763
1990	89.35532
1991	89.9705
1992	90.4209
1993	90.85714
1994	91.42053
1995	91.70124
1996	92.23433
1997	92.61745
1998	93.12169
1999	93.48958
2000	93.96662
2001	94.311
2002	94.76961
2003	95.21472
2004	95.64692
2005	96.06675
2006	96.47474
2007	96.75926
2008	97.14937
2009	97.6378
2010	98.00443
2011	98.25328
2012	98.60065
2013	98.93843
2014	99.26778
2015	99.5872