Year	Percent
1991	19.951
1992	19.827
1993	19.78
1994	19.835
1995	19.996
1996	20.104
1997	20.066
1998	20.076
1999	20.068
2000	20.01
2001	20.205
2002	20.369
2003	20.581
2004	19.621
2005	18.738
2006	18.577
2007	19.515
2008	19.558
2009	19.371
2010	20.482
2011	20.546
2012	20.604
2013	20.524
2014	20.466
2015	20.409
2016	20.172
2017	20.182
2018	20.195
2019	20.211
2020	20.231
2021	20.259
2022	20.293