Year	Percent
1992	91.44446
1993	92.10213
1994	91.91003
1995	91.96206
1996	92.49429
1997	92.58201
1998	92.87489
1999	93.09743
2000	93.50808
2001	93.82981
2002	94.08007
2003	93.74276
2004	93.98747
2005	94.01581
2006	93.66683
2007	93.82
2008	93.72751
2009	93.82152
2010	93.4412
2011	93.26674
2012	93.34734
2013	93.29232
2014	92.77961
2015	92.68997
2016	92.42024
2017	92.16959