Year	Percent
1991	72.327
1992	71.499
1993	70.758
1994	69.927
1995	69.739
1996	68.777
1997	67.839
1998	66.92
1999	66.081
2000	64.425
2001	63.485
2002	62.777
2003	62.117
2004	61.122
2005	60.957
2006	60.405
2007	60.133
2008	60.494
2009	61.311
2010	61.429
2011	62.912
2012	62.827
2013	63.098
2014	63.183
2015	63.302
2016	63.529
2017	63.723
2018	64.015
2019	64.283
2020	64.52
2021	64.752
2022	64.961