Year	Percent
1991	18.779
1992	11.601
1993	14.393
1994	16.84
1995	15.803
1996	16.497
1997	20.614
1998	18.608
1999	18.327
2000	16.183
2001	17.245
2002	16.074
2003	16.054
2004	14.294
2005	13.115
2006	13.343
2007	12.97
2008	12.974
2009	14.56
2010	13.835
2011	13.745
2012	13.861
2013	13.853
2014	14.363
2015	15.803
2016	16.005
2017	16.445
2018	16.453
2019	16.394
2020	16.349
2021	16.342
2022	16.329