Year	Percent
1991	58.823
1992	57.462
1993	55.552
1994	55.186
1995	56.109
1996	55.371
1997	56.403
1998	57.218
1999	57.386
2000	58.136
2001	58.595
2002	59.056
2003	59.213
2004	59.347
2005	58.936
2006	59.054
2007	58.455
2008	58.057
2009	57.552
2010	56.856
2011	55.141
2012	54.267
2013	53.764
2014	52.798
2015	52.165
2016	52.126
2017	51.981
2018	51.847
2019	51.703
2020	51.548
2021	51.384
2022	51.207