Year	Percent
1991	31.481
1992	34.719
1993	36.95
1994	38.333
1995	38.811
1996	34.497
1997	34.202
1998	33.594
1999	33.162
2000	32.263
2001	32.511
2002	32.744
2003	33.004
2004	33.403
2005	33.453
2006	33.892
2007	35.181
2008	33.698
2009	30.243
2010	29.069
2011	27.165
2012	26.975
2013	28.271
2014	29.063
2015	30.589
2016	33.286
2017	33.017
2018	32.047
2019	31.025
2020	29.967
2021	28.883
2022	27.813