Year	Percent
1991	29.144
1992	26.982
1993	25.199
1994	26.459
1995	24.306
1996	25.541
1997	23.218
1998	22.14
1999	20.724
2000	20.34
2001	20.86
2002	24.415
2003	24.043
2004	26.022
2005	24.765
2006	25.303
2007	24.656
2008	23.835
2009	21.938
2010	19.9
2011	19.872
2012	19.992
2013	20.089
2014	20.694
2015	20.028
2016	21.045
2017	20.388
2018	19.697
2019	19.254
2020	18.867
2021	18.659
2022	18.475