Year	Percent
1977	22.77433
1978	41.17873
1979	36.07964
1980	30.39989
1981	28.72509
1982	22.90913
1983	61.53215
1984	33.47979
1985	43.24193
1986	36.49278
1987	23.28969
1988	25.36508
1989	18.25005
1990	24.53145
1991	18.61137
1992	20.57526
1993	18.59116
1994	14.93248
1995	17.19441
1996	14.42563
1997	12.80843
1998	10.21149
1999	8.75931
2000	9.54251
2001	10.3271
2002	10.04227
2003	11.4394
2004	11.20011
2005	9.21705
2006	7.57924
2007	7.80833
2008	12.50673
2009	11.3288
2010	7.80108
2011	11.2949
2012	14.82416
2013	20.46536
2014	20.48995
2015	15.89884
2016	14.79594