Year	Percent
1979	89.50636
1980	91.44168
1981	90.51491
1982	90.50604
1983	90.15395
1984	90.95664
1985	90.87657
1986	90.12398
1987	89.50393
1988	91.19735
1989	91.36493
1991	92.46956
1992	92.4883
1993	92.9116
1994	92.41462
1995	93.1858
1996	91.90092
1997	91.80776
1998	91.67373
1999	90.4754
2001	90.5572
2002	90.62204
2003	90.47765
2004	90.33657
2006	89.88424
2007	89.93201
2008	90.06888
2011	89.56937
2012	89.241
2013	89.53819
2014	90.01592
2015	90.78893