Year	Percent
1991	69.77
1992	69.362
1993	69.161
1994	68.858
1995	68.405
1996	66.572
1997	63.619
1998	62.519
1999	61.756
2000	61.488
2001	59.716
2002	59.019
2003	58.815
2004	58.241
2005	58.236
2006	57.79
2007	57.301
2008	56.969
2009	57.351
2010	58.235
2011	57.891
2012	57.515
2013	57.777
2014	58.158
2015	58.905
2016	58.523
2017	57.664
2018	57.108
2019	56.9
2020	56.97
2021	56.461
2022	56.058