Year	Percent
1991	17.823
1992	17.774
1993	17.776
1994	18.026
1995	17.625
1996	17.684
1997	18.271
1998	17.665
1999	17.706
2000	17.101
2001	16.776
2002	17.32
2003	16.844
2004	16.567
2005	19.015
2006	17.772
2007	19.428
2008	18.76
2009	17.3
2010	15.152
2011	15.261
2012	14.838
2013	14.557
2014	14.118
2015	14.081
2016	13.385
2017	13.294
2018	13.126
2019	12.955
2020	12.786
2021	12.612
2022	12.441