Year	Percent
1991	42.309
1992	39.732
1993	39.546
1994	38.583
1995	36.65
1996	36.909
1997	36.208
1998	35.119
1999	34.298
2000	34.691
2001	35.668
2002	36.216
2003	38.187
2004	37.602
2005	38.156
2006	37.875
2007	38.034
2008	38.468
2009	36.784
2010	37.339
2011	37.343
2012	37.956
2013	38.007
2014	37.93
2015	37.652
2016	37.253
2017	37.148
2018	37.091
2019	37.069
2020	36.915
2021	36.857
2022	36.826