Year	Percent
1991	68.2
1992	67.591
1993	67.179
1994	66.806
1995	67.178
1996	65.991
1997	66.174
1998	66.715
1999	65.935
2000	65.402
2001	65.158
2002	64.875
2003	64.63
2004	63.953
2005	64.223
2006	63.816
2007	63.677
2008	63.517
2009	63.473
2010	62.897
2011	62.311
2012	62.17
2013	61.829
2014	61.59
2015	61.612
2016	61.684
2017	61.676
2018	61.673
2019	61.626
2020	61.562
2021	61.486
2022	61.431