Year	Percent
1980	96.39777
1981	96.41135
1982	95.19288
1983	93.2948
1984	93.21526
1985	94.21769
1986	91.57233
1987	90.07075
1988	90.56478
1989	91.51913
1990	90.3953
1991	88.76059
1992	90.05247
1993	89.87629
1994	90.62563
1995	89.1371
1996	90.0185
1997	89.85468
1998	89.98195
1999	90.53715
2000	89.9386
2001	90.78308
2002	87.61988
2003	87.00935
2004	87.45833
2005	85.88235
2006	84.5749
2007	84.07498
2008	85.11335
2009	86.96396
2010	86.90299
2011	87.43614