Year	Percent
1991	25.229
1992	24.882
1993	21.493
1994	20.546
1995	19.421
1996	16.704
1997	15.453
1998	17.495
1999	16.667
2000	16.449
2001	16.223
2002	15.996
2003	15.747
2004	15.507
2005	15.354
2006	15.21
2007	15.109
2008	14.595
2009	15.127
2010	14.927
2011	17.552
2012	18.044
2013	19.25
2014	18.43
2015	22.626
2016	21.043
2017	20.474
2018	19.849
2019	19.225
2020	18.677
2021	18.221
2022	17.863