Year	Percent
1991	30.679
1992	30.523
1993	29.968
1994	29.397
1995	29.112
1996	29.752
1997	27.566
1998	26.585
1999	25.417
2000	26.238
2001	31.388
2002	30.172
2003	27.102
2004	23.852
2005	20.729
2006	18.656
2007	20.909
2008	22.569
2009	24.099
2010	20.629
2011	20.864
2012	20.867
2013	20.857
2014	20.875
2015	20.982
2016	20.623
2017	20.579
2018	20.725
2019	20.883
2020	21.088
2021	21.295
2022	21.469