Year	Percent
1991	24.94
1992	24.05
1993	21.815
1994	19.326
1995	18.884
1996	17.808
1997	18.201
1998	17.668
1999	15.351
2000	18.568
2001	18.416
2002	17.117
2003	16.787
2004	15.552
2005	16.293
2006	15.106
2007	16.665
2008	20.773
2009	19.049
2010	16.894
2011	16.146
2012	15.801
2013	15.283
2014	14.291
2015	15.97
2016	18.599
2017	18.682
2018	18.818
2019	18.908
2020	18.829
2021	18.582
2022	18.126