Year	Percent
1991	15.885
1992	15.447
1993	14.988
1994	14.296
1995	14.365
1996	14.585
1997	13.922
1998	14.15
1999	14.729
2000	14.546
2001	16.636
2002	17.982
2003	17.463
2004	16.987
2005	16.851
2006	17.025
2007	15.812
2008	15.559
2009	15.651
2010	14.051
2011	14.126
2012	14.46
2013	14.44
2014	12.871
2015	12.507
2016	12.511
2017	12.493
2018	12.491
2019	12.488
2020	12.486
2021	12.484
2022	12.482