Year	Percent
1991	59.809
1992	52.591
1993	47.932
1994	44.253
1995	40.981
1996	39.951
1997	42.86
1998	46.335
1999	46.354
2000	46.991
2001	48.101
2002	47.655
2003	43.18
2004	41.334
2005	39.877
2006	39.085
2007	38.923
2008	38.084
2009	32.724
2010	29.898
2011	28.663
2012	24.657
2013	22.745
2014	22.771
2015	24.12
2016	25.635
2017	27.131
2018	28.303
2019	28.744
2020	28.795
2021	28.782
2022	28.754