Year	Percent
1990	47.79898
1991	39.14293
1992	43.18401
1993	30.53365
1994	20.55224
1995	36.82072
1996	34.17525
1997	30.0042
1998	22.79676
1999	18.40915
2000	21.52485
2001	27.64585
2002	29.34573
2003	30.57825
2004	32.65164
2005	28.66117
2006	30.94773
2007	36.52842
2008	38.55572
2009	34.72212
2010	28.51337
2011	30.84216
2012	32.48435
2013	30.88798
2014	27.08608
2015	21.34722
2016	20.69152
2017	29.54369