Year	Percent
1991	19.446
1992	19.202
1993	19.111
1994	17.986
1995	17.469
1996	16.221
1997	14.961
1998	14.142
1999	14.469
2000	14.656
2001	13.833
2002	12.013
2003	11.519
2004	10.808
2005	10.871
2006	11.202
2007	10.169
2008	9.651
2009	8.612
2010	8.321
2011	8.255
2012	8.139
2013	8.443
2014	13.11
2015	13.305
2016	13.208
2017	13.344
2018	13.559
2019	13.984
2020	13.918
2021	13.867
2022	13.739