Year	Percent
1991	18.531
1992	18.321
1993	18.562
1994	18.761
1995	18.233
1996	18.246
1997	16.545
1998	15.682
1999	14.903
2000	13.728
2001	12.848
2002	12.04
2003	11.713
2004	11.779
2005	11.699
2006	11.682
2007	11.662
2008	11.53
2009	11.918
2010	11.582
2011	11.401
2012	11.304
2013	11.166
2014	11.232
2015	11.053
2016	10.989
2017	11.008
2018	10.977
2019	10.819
2020	10.669
2021	10.528
2022	10.391