Year	Percent
1991	52.462
1992	51.872
1993	50.987
1994	50.064
1995	49.502
1996	48.704
1997	48.254
1998	47.951
1999	47.412
2000	46.55
2001	45.875
2002	44.818
2003	43.554
2004	42.341
2005	41.326
2006	40.474
2007	39.784
2008	39.184
2009	38.641
2010	37.957
2011	37.178
2012	36.457
2013	35.694
2014	34.926
2015	34.19
2016	33.569
2017	33.329
2018	33.116
2019	32.918
2020	32.734
2021	32.547
2022	32.374