Year	Percent
1991	9.606
1992	9.251
1993	9.489
1994	9.463
1995	9.518
1996	9.115
1997	10.993
1998	12.833
1999	14.636
2000	16.578
2001	16.147
2002	16.259
2003	16.197
2004	16.348
2005	16.102
2006	15.882
2007	16.273
2008	17.128
2009	17.462
2010	17.509
2011	17.469
2012	16.601
2013	16.24
2014	16.063
2015	15.417
2016	15.342
2017	15.599
2018	15.222
2019	15.036
2020	14.902
2021	14.753
2022	14.615