Year	Percent
1991	61.06
1992	60.901
1993	58.849
1994	58.895
1995	59.319
1996	60.022
1997	60.569
1998	60.671
1999	60.039
2000	60.227
2001	59.835
2002	59.749
2003	58.919
2004	58.017
2005	57.095
2006	56.305
2007	56.285
2008	55.511
2009	56.377
2010	53.808
2011	55.111
2012	56.887
2013	51.695
2014	51.649
2015	54.059
2016	54.836
2017	55.595
2018	54.726
2019	54.709
2020	54.73
2021	54.696
2022	54.641