Year	Percent
1991	71.79148
1992	71.37826
1993	70.85286
1994	70.2365
1995	69.80537
1996	69.1887
1997	68.57776
1998	68.21237
1999	67.95212
2000	67.93401
2001	67.48536
2002	67.41019
2003	67.72125
2004	67.78682
2005	67.75725
2006	67.8265
2007	67.68712
2008	68.03049
2009	67.65596
2010	67.28941
2011	66.52176
2012	66.0805
2013	66.31734
2014	64.92655
2015	65.4623
2016	64.64016
2017	64.87126
2018	63.74396
2019	63.10536