Year	Percent
1991	17.027
1992	17.237
1993	18.778
1994	18.809
1995	18.607
1996	18.931
1997	18.338
1998	18.559
1999	19.437
2000	19.641
2001	21.595
2002	22.726
2003	24.398
2004	21.542
2005	20.555
2006	20.891
2007	21.12
2008	22.049
2009	22.687
2010	22.118
2011	25.332
2012	21.218
2013	26.296
2014	29.457
2015	32.109
2016	32.247
2017	27.839
2018	25.822
2019	24.488
2020	22.901
2021	22.109
2022	21.731