Year	Percent
1991	68.978
1992	68.48
1993	68.067
1994	67.554
1995	66.944
1996	66.32
1997	64.265
1998	64.707
1999	64.289
2000	63.885
2001	62.664
2002	63.209
2003	62.536
2004	62.726
2005	61.819
2006	60.962
2007	60.067
2008	59.891
2009	59.635
2010	59.022
2011	59.976
2012	60.48
2013	60.494
2014	61.051
2015	61.468
2016	59.187
2017	58.658
2018	57.737
2019	56.771
2020	55.9
2021	55.114
2022	54.425