Year	Percent
1991	31.401
1992	31.673
1993	31.991
1994	32.137
1995	32.426
1996	32.699
1997	33.373
1998	34.124
1999	34.839
2000	35.519
2001	35.277
2002	34.004
2003	33.145
2004	32.688
2005	32.31
2006	31.161
2007	30.339
2008	29.622
2009	29.024
2010	28.373
2011	27.643
2012	26.954
2013	26.232
2014	23.872
2015	22.809
2016	21.385
2017	20.972
2018	20.764
2019	20.945
2020	21.54
2021	22.115
2022	22.561