Year	Percent
1991	17.499
1992	16.149
1993	17.018
1994	17.041
1995	18.231
1996	18.925
1997	18.57
1998	17.526
1999	18.871
2000	18.512
2001	19.273
2002	18.928
2003	18.754
2004	19.149
2005	18.715
2006	18.999
2007	19.267
2008	18.175
2009	18.76
2010	18.206
2011	16.767
2012	17.493
2013	18.363
2014	20.602
2015	20.793
2016	19.769
2017	19.451
2018	19.254
2019	19.074
2020	18.98
2021	18.867
2022	18.631