Year	Percent
1991	60.617
1992	60.31
1993	60.14
1994	59.901
1995	59.681
1996	59.498
1997	59.342
1998	59.168
1999	58.774
2000	58.262
2001	57.791
2002	57.283
2003	56.699
2004	56.121
2005	55.538
2006	54.949
2007	54.405
2008	53.939
2009	53.454
2010	53.008
2011	52.716
2012	52.372
2013	51.999
2014	51.639
2015	51.295
2016	50.982
2017	50.793
2018	50.609
2019	50.436
2020	50.281
2021	50.142
2022	50.022