Year	Percent
1991	28.659
1992	27.489
1993	28.711
1994	27.887
1995	25.084
1996	25.629
1997	24.922
1998	24.453
1999	24.114
2000	23.575
2001	23.851
2002	21.943
2003	21.376
2004	21.115
2005	20.643
2006	19.883
2007	19.164
2008	19.294
2009	19.961
2010	20.23
2011	19.92
2012	19.319
2013	18.892
2014	20.127
2015	20.451
2016	20.101
2017	19.694
2018	19.634
2019	19.578
2020	19.528
2021	19.486
2022	19.451