Year	Percent
1991	68.588
1992	68.102
1993	67.831
1994	67.44
1995	67.448
1996	67.218
1997	67.055
1998	66.823
1999	65.351
2000	65.139
2001	64.874
2002	65.158
2003	64.899
2004	64.753
2005	64.09
2006	63.427
2007	62.87
2008	62.392
2009	61.54
2010	61.24
2011	63.8
2012	63.235
2013	62.483
2014	61.843
2015	61.271
2016	60.451
2017	60.289
2018	60.216
2019	60.145
2020	60.077
2021	60.007
2022	59.938