Year	Percent
1991	42.675
1992	41.066
1993	40.659
1994	38.934
1995	38.397
1996	38.654
1997	38.165
1998	37.904
1999	36.89
2000	36.221
2001	35.774
2002	35.037
2003	34.398
2004	33.115
2005	33.107
2006	32.802
2007	32.967
2008	32.709
2009	29.982
2010	29.445
2011	29.299
2012	28.936
2013	28.591
2014	28.568
2015	28.218
2016	27.927
2017	27.801
2018	27.642
2019	27.516
2020	27.437
2021	27.338
2022	27.24