Year	Percent
1991	21.626
1992	24.173
1993	23.516
1994	23.814
1995	22.7
1996	21.93
1997	20.26
1998	24.218
1999	23.279
2000	22.874
2001	22.143
2002	21.086
2003	20.655
2004	19.376
2005	18.434
2006	18.643
2007	18.101
2008	16.617
2009	16.017
2010	15.949
2011	15.788
2012	14.814
2013	14.744
2014	14.986
2015	15.234
2016	15.145
2017	15.47
2018	15.113
2019	14.802
2020	14.537
2021	14.256
2022	14.085