Year	Percent
1991	69.664
1992	69.72
1993	68.097
1994	67.338
1995	66.72
1996	66.698
1997	65.6
1998	70.806
1999	78.355
2000	70.504
2001	63.059
2002	55.723
2003	49.702
2004	42.164
2005	36.385
2006	30.626
2007	24.97
2008	18.292
2009	18.158
2010	18.575
2011	17.875
2012	17.535
2013	17.229
2014	16.903
2015	16.105
2016	15.697
2017	15.265
2018	14.905
2019	14.609
2020	14.208
2021	13.792
2022	13.365