Year	Percent
1991	38.131
1992	36.745
1993	34.005
1994	32.924
1995	32.205
1996	31.454
1997	30.588
1998	29.296
1999	27.748
2000	27.496
2001	26.518
2002	25.445
2003	24.317
2004	22.317
2005	22.144
2006	21.816
2007	21.196
2008	20.643
2009	21.019
2010	20.633
2011	20.533
2012	20.073
2013	20.667
2014	21.192
2015	21.149
2016	21.084
2017	20.911
2018	20.838
2019	20.767
2020	20.657
2021	20.497
2022	20.369