Year	Percent
1991	22.1287
1992	21.98672
1993	21.90978
1994	21.80369
1995	21.70809
1996	21.49295
1997	21.26454
1998	21.00111
1999	20.66241
2000	20.30303
2001	19.9181
2002	19.71903
2003	19.29718
2004	18.74994
2005	18.5252
2006	19.43818
2007	18.70206
2008	18.02176
2009	18.47126
2010	17.94613
2011	16.36117
2012	17.07378
2013	15.3648
2014	14.84137
2015	14.67877
2016	14.70907
2017	14.74364
2018	14.20819
2019	13.73214