Year	Percent
1991	62.111
1992	60.281
1993	59.257
1994	57.609
1995	56.561
1996	56.243
1997	55.976
1998	55.909
1999	56.038
2000	56.135
2001	56.438
2002	56.946
2003	57.323
2004	57.878
2005	57.203
2006	57.416
2007	57.404
2008	56.967
2009	55.449
2010	54.527
2011	54.136
2012	53.226
2013	51.611
2014	51.376
2015	51.799
2016	52.317
2017	52.303
2018	52.299
2019	52.045
2020	51.768
2021	51.427
2022	51.061