Year	Percent
1991	19.521
1992	20.443
1993	21.416
1994	20.369
1995	20.014
1996	17.962
1997	16.087
1998	14.454
1999	15.605
2000	16.037
2001	14.702
2002	14.629
2003	15.143
2004	13.804
2005	12.605
2006	11.505
2007	10.556
2008	11.211
2009	10.157
2010	10.339
2011	8.081
2012	7.99
2013	7.864
2014	7.727
2015	7.473
2016	7.512
2017	7.334
2018	7.177
2019	7.016
2020	6.871
2021	6.828
2022	6.783