Year	Percent
1991	13.076
1992	13.61
1993	13.068
1994	13.745
1995	14.141
1996	14.857
1997	14.462
1998	14.643
1999	13.806
2000	15.153
2001	15.176
2002	14.776
2003	14.772
2004	14.731
2005	13.035
2006	14.115
2007	12.082
2008	10.843
2009	11.053
2010	9.669
2011	8.426
2012	8.184
2013	7.036
2014	6.729
2015	5.996
2016	6.013
2017	5.655
2018	5.621
2019	5.601
2020	5.583
2021	5.566
2022	5.551