Year	Percent
1991	34.42055
1992	34.08654
1993	33.82603
1994	33.57663
1995	33.1805
1996	32.78998
1997	32.40364
1998	32.03092
1999	31.73552
2000	31.07375
2001	30.28745
2002	29.83883
2003	29.33562
2004	28.74778
2005	28.24547
2006	27.56872
2007	27.06823
2008	26.11026
2009	25.35543
2010	24.44352
2011	23.71918
2012	22.9704
2013	22.09679
2014	20.84597
2015	19.87986
2016	19.0902
2017	18.47414
2018	17.97873
2019	17.62915