Year	Percent
1990	45.87947
1991	42.23876
1992	43.14005
1993	39.03712
1994	42.73284
1995	36.16832
1996	37.54525
1997	35.73773
1998	31.9959
1999	30.1986
2000	30.1137
2001	32.08147
2002	33.24871
2003	30.94589
2004	31.31564
2005	31.86336
2006	32.57161
2007	34.06777
2008	36.79514
2009	36.42079
2010	37.48004
2011	38.32461
2012	32.54576
2013	32.23753
2014	31.51692
2015	29.94372
2016	30.22158
2017	30.05665