Year	Percent
1990	27.39136
1991	26.16144
1992	27.46039
1993	25.66215
1994	27.57413
1995	22.57692
1996	18.15761
1997	17.44056
1998	21.1747
1999	17.44471
2000	14.46692
2001	14.93853
2002	14.31415
2003	13.74497
2004	12.41537
2005	11.09324
2006	10.70558
2007	10.41929
2008	10.19686
2009	10.01907
2010	9.87371
2011	9.75264
2012	16.99033
2013	17.68498
2014	17.67657
2015	20.20594
2016	25.09091
2017	26.96107
2018	28.74514