Year	Percent
1991	71.82009
1992	72.076
1993	72.38428
1994	72.58752
1995	72.61315
1996	72.63289
1997	72.88514
1998	72.93332
1999	73.13714
2000	73.45427
2001	73.41515
2002	73.16882
2003	72.80577
2004	72.32179
2005	71.87039
2006	71.4477
2007	70.9242
2008	70.43814
2009	70.09145
2010	69.5349
2011	68.95638
2012	68.33674
2013	67.61083
2014	66.80566
2015	66.1473
2016	65.80582
2017	65.37719
2018	64.81141
2019	64.31813