Year	Percent
1991	17.233
1992	17.076
1993	16.937
1994	16.8
1995	16.563
1996	16.46
1997	16.3
1998	16.18
1999	16.045
2000	15.981
2001	15.873
2002	15.67
2003	15.521
2004	15.361
2005	15.158
2006	15.006
2007	14.882
2008	14.812
2009	14.652
2010	14.58
2011	14.515
2012	14.322
2013	14.168
2014	14.076
2015	14.024
2016	13.966
2017	13.971
2018	13.973
2019	13.974
2020	13.972
2021	13.968
2022	13.96