Year	Percent
1991	67.71
1992	68.088
1993	68.96
1994	68.851
1995	67.733
1996	66.838
1997	66.866
1998	65.997
1999	66.214
2000	66.361
2001	66.288
2002	66.461
2003	66.209
2004	67.052
2005	67.017
2006	65.367
2007	63.764
2008	63.035
2009	63.406
2010	63.506
2011	62.444
2012	61.563
2013	61.379
2014	61.218
2015	60.11
2016	60.406
2017	59.765
2018	59.644
2019	59.385
2020	59.078
2021	58.779
2022	58.488