Year	Percent
1991	57.091
1992	55.249
1993	55.822
1994	58.701
1995	57.5
1996	60.081
1997	52.999
1998	49.823
1999	46.054
2000	43.884
2001	42.982
2002	45.136
2003	44.102
2004	41.989
2005	41.175
2006	38.291
2007	36.762
2008	36.198
2009	36.584
2010	35.078
2011	34.21
2012	33.474
2013	32.741
2014	31.501
2015	30.573
2016	30.665
2017	30.835
2018	30.413
2019	30.133
2020	29.787
2021	29.418
2022	29.027