Year	Percent
1991	15.594
1992	17.395
1993	16.921
1994	14.187
1995	14.483
1996	15.512
1997	15.887
1998	16.333
1999	15.359
2000	14.358
2001	14.663
2002	16.648
2003	19.341
2004	21.217
2005	20.148
2006	20.507
2007	21.916
2008	18.327
2009	19.568
2010	20.975
2011	21.5
2012	21.909
2013	22.221
2014	21.963
2015	21.795
2016	22.114
2017	21.775
2018	21.357
2019	21.31
2020	21.456
2021	21.501
2022	21.573