Year	Percent
1991	35.217
1992	34.899
1993	34.138
1994	34.015
1995	29.076
1996	29.852
1997	25.209
1998	27.843
1999	26.151
2000	26.116
2001	16.856
2002	17.73
2003	18.271
2004	20.829
2005	17.759
2006	17.674
2007	18.369
2008	18.817
2009	18.953
2010	18.656
2011	18.78
2012	19.257
2013	19.085
2014	19.016
2015	18.816
2016	19.173
2017	19.617
2018	19.546
2019	19.358
2020	19.047
2021	18.644
2022	18.237