Year	Percent
1991	69.84
1992	72.091
1993	76.817
1994	80.423
1995	77.232
1996	77.504
1997	77.851
1998	78.018
1999	78.097
2000	78.091
2001	77.926
2002	73.169
2003	72.292
2004	70.229
2005	70.217
2006	69.07
2007	67.918
2008	65.79
2009	65.375
2010	62.814
2011	61.086
2012	59.859
2013	59.599
2014	59.65
2015	58.997
2016	59.122
2017	59.902
2018	59.654
2019	59.342
2020	59.026
2021	58.588
2022	58.152