Year	Percent
1991	25.06165
1992	25.57136
1993	26.34741
1994	25.89223
1995	25.49841
1996	25.35432
1997	25.32567
1998	26.47844
1999	27.34332
2000	27.28138
2001	26.01019
2002	24.77667
2003	23.58611
2004	22.32812
2005	21.08569
2006	19.8579
2007	18.7368
2008	18.56305
2009	18.71439
2010	18.59181
2011	19.68627
2012	19.23733
2013	18.56951
2014	18.84787
2015	18.60266
2016	18.28461
2017	17.93706
2018	17.62809
2019	17.34381