Year	Percent
1991	33.782
1992	33.897
1993	34.072
1994	34.324
1995	34.023
1996	33.712
1997	33.405
1998	33.099
1999	32.798
2000	32.52
2001	32.996
2002	33.478
2003	33.963
2004	34.458
2005	34.943
2006	33.32
2007	31.747
2008	30.229
2009	28.745
2010	27.304
2011	26.477
2012	25.677
2013	25.834
2014	26.003
2015	26.126
2016	26.306
2017	26.077
2018	25.845
2019	25.612
2020	25.379
2021	25.142
2022	24.905