Year	Percent
1991	19.711
1992	19.064
1993	18.311
1994	17.776
1995	17.576
1996	17.506
1997	17.785
1998	18.213
1999	18.509
2000	18.517
2001	15.068
2002	14.645
2003	14.002
2004	14.319
2005	13.629
2006	13.749
2007	14.171
2008	14.599
2009	15.041
2010	15.348
2011	15.494
2012	15.573
2013	15.368
2014	15.127
2015	14.871
2016	14.629
2017	14.495
2018	14.403
2019	14.335
2020	14.285
2021	14.27
2022	14.276