Year	Percent
1991	74.06
1992	73.737
1993	74.075
1994	72.842
1995	71.252
1996	69.498
1997	68.408
1998	67.636
1999	69.525
2000	70.223
2001	69.565
2002	69.474
2003	70.909
2004	70.001
2005	66.473
2006	65.794
2007	67.308
2008	67.859
2009	66.727
2010	65.506
2011	63.63
2012	61.395
2013	60.352
2014	60.328
2015	58.424
2016	58.079
2017	58.028
2018	57.94
2019	57.85
2020	57.759
2021	57.668
2022	57.577