Year	Percent
1991	84.43651
1992	84.54836
1993	84.36464
1994	84.23389
1995	84.16816
1996	83.81776
1997	83.41551
1998	82.97137
1999	82.40873
2000	82.2206
2001	81.51989
2002	80.9442
2003	80.46968
2004	79.9766
2005	79.51447
2006	78.86035
2007	78.26532
2008	77.66018
2009	77.05956
2010	76.39947
2011	75.64172
2012	74.84068
2013	74.00735
2014	73.10657
2015	72.1162
2016	71.56064
2017	71.05727
2018	70.57779
2019	70.21834