Year	Percent
1991	30.349
1992	29.791
1993	30.176
1994	30.141
1995	29.898
1996	21.302
1997	21.033
1998	20.797
1999	20.698
2000	20.229
2001	20.29
2002	20.217
2003	19.865
2004	19.782
2005	19.383
2006	19.223
2007	20.211
2008	19.678
2009	19.837
2010	20.124
2011	19.267
2012	20.322
2013	21.474
2014	21.173
2015	20.959
2016	20.627
2017	20.483
2018	20.429
2019	20.376
2020	20.322
2021	20.268
2022	20.214