Year	Percent
1977	17.52929
1978	27.27728
1979	18.51275
1980	20.67271
1981	25.62638
1982	18.33493
1983	19.37063
1984	21.03729
1985	27.91391
1986	32.32131
1987	25.18183
1988	18.93677
1989	13.89977
1990	10.61927
1991	10.74606
1992	9.86071
1993	8.7238
1994	10.07368
1995	6.57414
1996	5.76375
1997	5.43703
1998	4.64442
1999	5.7405
2004	5.50175
2005	3.94974
2006	4.55851
2007	3.70018
2008	4.16687
2009	4.69519
2010	5.26605
2011	5.61736
2012	5.6049
2013	5.98136
2014	7.84216
2015	9.3806
2016	8.73128