Year	Percent
1991	27.749
1992	25.425
1993	23.798
1994	22.124
1995	20.826
1996	20.401
1997	19.858
1998	20.055
1999	20.432
2000	21.644
2001	22.005
2002	20.967
2003	20.506
2004	22.465
2005	20.623
2006	19.933
2007	19.548
2008	19.353
2009	16.962
2010	16.301
2011	15.341
2012	14.764
2013	13.443
2014	12.553
2015	12.277
2016	13.648
2017	13.999
2018	14.267
2019	14.201
2020	14.014
2021	13.817
2022	13.635