Year	Percent
1991	20.274
1992	20.001
1993	19.608
1994	19.161
1995	18.929
1996	18.121
1997	19.136
1998	20.412
1999	22.006
2000	24.825
2001	25.999
2002	26.225
2003	27.264
2004	27.594
2005	27.34
2006	26.175
2007	25.831
2008	26.062
2009	20.752
2010	20.955
2011	27.616
2012	29.96
2013	31.843
2014	34.525
2015	34.506
2016	34.597
2017	34.546
2018	34.508
2019	34.521
2020	34.543
2021	34.564
2022	34.589