Year	Percent
1991	68.218
1992	66.822
1993	64.159
1994	61.884
1995	59.6
1996	57.835
1997	56.919
1998	56.394
1999	55.79
2000	54.985
2001	54.167
2002	53.093
2003	51.395
2004	49.288
2005	47.652
2006	45.966
2007	44.241
2008	42.487
2009	41.595
2010	40.229
2011	39
2012	38.219
2013	37.635
2014	37.056
2015	36.787
2016	36.377
2017	36.353
2018	36.283
2019	36.217
2020	36.154
2021	36.093
2022	36.033