Year	Percent
1991	42.114
1992	48.93
1993	48.718
1994	46.998
1995	44.226
1996	40.823
1997	35.251
1998	32.078
1999	36.999
2000	38.232
2001	37.255
2002	36.872
2003	35.071
2004	36.018
2005	35.908
2006	36.222
2007	37.103
2008	40.468
2009	37.835
2010	38.111
2011	38.799
2012	37.305
2013	37.934
2014	36.789
2015	35.176
2016	34.787
2017	33.601
2018	32.169
2019	30.95
2020	30.04
2021	29.405
2022	29.125