Year	Percent
1991	18.446
1992	18.487
1993	16.651
1994	17.26
1995	17.277
1996	16.216
1997	17.185
1998	16.47
1999	15.555
2000	15.297
2001	14.768
2002	13.424
2003	12.96
2004	13.228
2005	11.903
2006	11.382
2007	10.666
2008	9.924
2009	9.383
2010	8.769
2011	8.73
2012	8.74
2013	8.738
2014	8.447
2015	8.512
2016	8.972
2017	8.47
2018	8.262
2019	8.115
2020	8.018
2021	7.928
2022	7.861