Year	Percent
1991	86.81329
1992	86.64408
1993	86.33889
1994	85.95674
1995	85.41293
1996	84.67341
1997	84.09533
1998	83.27647
1999	82.62283
2000	81.87043
2001	81.05302
2002	80.30297
2003	79.37413
2004	78.2949
2005	77.20785
2006	76.47635
2007	75.05898
2008	73.78985
2009	72.65475
2010	71.46068
2011	70.31119
2012	69.04371
2013	67.77069
2014	66.70177
2015	65.57961
2016	64.71249
2017	63.58359
2018	62.3719
2019	61.44352