Year	Percent
1991	33.08
1992	33.337
1993	33.223
1994	34.117
1995	34.139
1996	34.29
1997	35.84
1998	37.291
1999	37.592
2000	38.493
2001	39.217
2002	38.424
2003	38.724
2004	37.949
2005	39.353
2006	39.888
2007	39.932
2008	36.556
2009	31.405
2010	28.776
2011	27.619
2012	26.526
2013	26.215
2014	26.369
2015	27.84
2016	28.404
2017	28.056
2018	27.88
2019	27.748
2020	27.691
2021	27.641
2022	27.65