Year	Percent
1991	21.676
1992	14.798
1993	15.706
1994	15.905
1995	18.654
1996	20.111
1997	20.526
1998	19.584
1999	20.485
2000	19.7
2001	20.211
2002	20.805
2003	20.962
2004	18.865
2005	17.183
2006	17.011
2007	14.591
2008	11.701
2009	11.995
2010	10.901
2011	10.614
2012	11.076
2013	11.795
2014	12.127
2015	12.296
2016	12.362
2017	12.645
2018	12.637
2019	12.628
2020	12.606
2021	12.594
2022	12.584