Year	Percent
1991	17.761
1992	17.515
1993	17.348
1994	17.109
1995	16.919
1996	16.737
1997	16.376
1998	16.067
1999	15.729
2000	15.503
2001	15.332
2002	15.223
2003	15.059
2004	14.904
2005	14.706
2006	14.491
2007	14.429
2008	14.364
2009	14.589
2010	14.837
2011	14.848
2012	14.848
2013	14.795
2014	14.751
2015	14.616
2016	14.573
2017	14.543
2018	14.534
2019	14.495
2020	14.443
2021	14.367
2022	14.286