Year	Percent
1991	38.082
1992	37.926
1993	37.611
1994	37.283
1995	36.824
1996	36.344
1997	35.754
1998	35.088
1999	34.29
2000	33.426
2001	32.3
2002	31.107
2003	29.831
2004	28.664
2005	27.517
2006	26.576
2007	25.75
2008	24.994
2009	24.319
2010	23.587
2011	23.06
2012	22.618
2013	22.172
2014	21.762
2015	21.386
2016	20.929
2017	20.785
2018	20.628
2019	20.461
2020	20.285
2021	20.103
2022	19.909