Year	Percent
1991	19.575
1992	19.913
1993	20.128
1994	21.559
1995	22.344
1996	23.252
1997	21.854
1998	23.596
1999	23.007
2000	23.062
2001	25.947
2002	24.899
2003	26.322
2004	26.535
2005	24.08
2006	18.904
2007	19.304
2008	19.914
2009	20.548
2010	20.781
2011	20.134
2012	20.246
2013	19.646
2014	20.065
2015	18.709
2016	18.703
2017	19.103
2018	18.797
2019	18.805
2020	18.81
2021	18.779
2022	18.779