Year	Percent
1991	18.866
1992	21.147
1993	17.327
1994	19.349
1995	19.49
1996	20.197
1997	20.561
1998	21.457
1999	21.434
2000	20.523
2001	18.225
2002	19.858
2003	20.587
2004	21.359
2005	20.393
2006	20.035
2007	20.547
2008	21.998
2009	19.827
2010	20.558
2011	19.852
2012	19.001
2013	20.383
2014	20.73
2015	20.689
2016	19.679
2017	18.273
2018	18.375
2019	18.392
2020	18.411
2021	18.395
2022	18.414