Year	Percent
1991	20.199
1992	19.468
1993	20.529
1994	18.726
1995	18.53
1996	17.561
1997	16.981
1998	16.881
1999	16.039
2000	16.235
2001	16.941
2002	16.891
2003	16.648
2004	16.993
2005	16.746
2006	16.273
2007	15.818
2008	15.529
2009	15.862
2010	15.512
2011	16.096
2012	16.015
2013	14.836
2014	14.372
2015	13.731
2016	13.194
2017	13.357
2018	13.115
2019	13.011
2020	12.89
2021	12.776
2022	12.635