Year	Percent
1981	83.68374
1983	87.36091
1984	88.09742
1985	86.30827
1986	84.00007
1987	84.65358
1988	85.01449
1989	86.64166
1998	81.57426
1999	83.73157
2001	95.51838
2002	90.73523
2003	91.46141
2004	90.46289
2005	89.83842
2006	87.51178
2007	88.14824
2008	88.94004
2009	88.8018
2013	96.53496
2015	98.77573