Year	Percent
1991	20.718
1992	19.98
1993	19.262
1994	19.042
1995	18.808
1996	18.456
1997	18.48
1998	18.244
1999	18.405
2000	18.104
2001	17.77
2002	17.608
2003	17.501
2004	17.474
2005	17.302
2006	16.624
2007	16.305
2008	16.113
2009	15.974
2010	15.777
2011	15.367
2012	12.629
2013	12.463
2014	12.421
2015	12.154
2016	11.735
2017	12.075
2018	11.849
2019	11.79
2020	11.706
2021	11.684
2022	11.593