Year	Percent
1991	33.64007
1992	33.62154
1993	33.58421
1994	33.52226
1995	33.41186
1996	33.27533
1997	33.0854
1998	32.8711
1999	32.65685
2000	32.39144
2001	32.08976
2002	31.75872
2003	31.38281
2004	30.89981
2005	30.37063
2006	29.77885
2007	29.13459
2008	28.51561
2009	27.99724
2010	27.3298
2011	26.67667
2012	25.99338
2013	25.33157
2014	24.63289
2015	23.9646
2016	23.26351
2017	22.54701
2018	21.81054
2019	21.08449