Year	Percent
1991	19.497
1992	19.049
1993	18.922
1994	18.782
1995	18.924
1996	18.538
1997	17.569
1998	18.708
1999	18.121
2000	17.729
2001	17.085
2002	17.188
2003	13.303
2004	13.302
2005	14.263
2006	14.559
2007	13.564
2008	12.469
2009	11.867
2010	12.632
2011	12.539
2012	12.407
2013	12.564
2014	12.624
2015	12.412
2016	11.97
2017	11.854
2018	11.724
2019	11.651
2020	11.591
2021	11.523
2022	11.464