Year	Percent
1991	37.07
1992	38.303
1993	36.976
1994	34.812
1995	39.325
1996	37.141
1997	38.724
1998	36.063
1999	36.301
2000	35.294
2001	33.146
2002	31.643
2003	38.495
2004	36.713
2005	38.663
2006	42.27
2007	44.355
2008	42.695
2009	29.926
2010	26.916
2011	28.675
2012	32.007
2013	33.202
2014	36.736
2015	37.691
2016	35.235
2017	35.067
2018	33.455
2019	31.671
2020	30.194
2021	29.162
2022	28.518