Year	Percent
1991	29.116
1992	32.097
1993	31.761
1994	31.644
1995	31.258
1996	29.551
1997	29.809
1998	28.281
1999	28.725
2000	28.895
2001	29.691
2002	27.264
2003	26.854
2004	24.846
2005	24.376
2006	24.717
2007	22.723
2008	22.677
2009	19.939
2010	20.465
2011	20.317
2012	20.342
2013	19.94
2014	19.719
2015	19.239
2016	19.977
2017	19.854
2018	19.4
2019	19.041
2020	18.715
2021	18.372
2022	18.064