Year	Percent
1991	82.33781
1992	82.10355
1993	81.74681
1994	81.15164
1995	80.5168
1996	79.67516
1997	78.65746
1998	77.52304
1999	76.11239
2000	75.2521
2001	74.58731
2002	74.19276
2003	73.61438
2004	73.08483
2005	72.63815
2006	72.20902
2007	71.78355
2008	71.12941
2009	70.60878
2010	70.04178
2011	69.53413
2012	68.85733
2013	68.22957
2014	67.4659
2015	66.91713
2016	66.65637
2017	65.80225
2018	65.06429
2019	64.37738