Year	Percent
1991	64.914
1992	65.646
1993	65.914
1994	66.409
1995	66.834
1996	66.383
1997	65.526
1998	64.786
1999	64.099
2000	63.342
2001	62.395
2002	61.142
2003	60.345
2004	59.667
2005	58.945
2006	59.179
2007	59.39
2008	59.805
2009	59.98
2010	60.329
2011	60.469
2012	60.707
2013	60.917
2014	60.925
2015	60.868
2016	60.502
2017	60.331
2018	60.165
2019	60.031
2020	59.936
2021	59.884
2022	59.867