Year	Percent
1991	77.598
1992	77.431
1993	75.827
1994	74.124
1995	72.329
1996	70.431
1997	68.446
1998	66.377
1999	64.233
2000	62.02
2001	59.758
2002	57.421
2003	55.029
2004	52.628
2005	50.231
2006	47.834
2007	45.457
2008	43.111
2009	40.812
2010	38.615
2011	38.871
2012	38.639
2013	38.352
2014	38.028
2015	37.676
2016	37.463
2017	37.234
2018	36.991
2019	36.733
2020	36.462
2021	36.183
2022	35.885