Year	Percent
1991	12.476
1992	12.711
1993	13.503
1994	13.953
1995	14.573
1996	15.288
1997	14.801
1998	14.404
1999	13.821
2000	13.496
2001	13.082
2002	12.562
2003	12.153
2004	11.712
2005	11.32
2006	10.944
2007	10.533
2008	10.106
2009	9.616
2010	9.678
2011	9.405
2012	9.246
2013	9.217
2014	9.087
2015	8.926
2016	8.797
2017	8.65
2018	8.51
2019	8.363
2020	8.212
2021	8.061
2022	7.908