Year	Percent
1983	15.2538
1984	15.6882
1985	15.3418
1986	16.2216
1987	15.4246
1988	13.7969
1989	12.006
1990	10.3056
1991	9.8094
1992	8.801
1993	9.8694
1994	11.1866
1995	11.0794
1996	11.3115
1997	10.1981
1998	10.7005
1999	8.9667
2000	7.3924
2001	6.1328
2002	7.2037
2003	7.4141
2004	7.3511
2005	8.39
2006	8.1193
2007	7.3634
2008	6.6006
2009	6.8835
2010	7.4599
2011	6.3238
2012	6.5993
2013	7.1754
2014	6.9694
2015	7.1388
2016	6.8741
2017	6.215