Year	Percent
1991	41.663
1992	41.745
1993	41.652
1994	41.048
1995	40.76
1996	40.732
1997	40.196
1998	40.12
1999	40.287
2000	40.525
2001	40.161
2002	39.361
2003	38.41
2004	36.522
2005	33.672
2006	34.057
2007	36.263
2008	38.062
2009	36.338
2010	34.219
2011	32.507
2012	32.276
2013	33.459
2014	35.416
2015	35.71
2016	38.72
2017	38.973
2018	39.179
2019	39.345
2020	39.457
2021	39.523
2022	39.551