Year	Percent
1991	61.43945
1992	61.47884
1993	61.39951
1994	61.08156
1995	60.91901
1996	60.52399
1997	60.31
1998	60.08005
1999	60.03089
2000	60.61569
2001	60.99794
2002	61.89843
2003	62.948
2004	63.66988
2005	64.50705
2006	64.71445
2007	65.54084
2008	66.4874
2009	66.06684
2010	65.5401
2011	65.86276
2012	65.99363
2013	66.77039
2014	67.24112
2015	67.05807
2016	66.87189
2017	66.4724
2018	66.01336
2019	66.18819