Year	Percent
1991	13.522
1992	13.129
1993	13.928
1994	14.485
1995	14.446
1996	13.718
1997	13.206
1998	13.294
1999	12.246
2000	12.266
2001	12.01
2002	11.667
2003	11.098
2004	11.399
2005	10.518
2006	10.447
2007	10.093
2008	10.31
2009	9.876
2010	9.72
2011	9.378
2012	9.238
2013	9.294
2014	9.653
2015	10.108
2016	8.972
2017	9.068
2018	8.94
2019	8.772
2020	8.672
2021	8.578
2022	8.523