Year	Percent
1974	6.55033
1975	6.05175
1976	6.33999
1977	6.78851
1978	16.53786
1979	17.67168
1980	31.2352
1981	18.24259
1982	13.65902
1983	11.96972
1984	17.63135
1985	22.15223
1986	27.82771
1987	34.42759
1988	33.43924
1989	30.27548
1990	21.09065
1991	22.65716
1992	14.55648
1993	10.27226
1994	18.09661
1995	17.75815
1996	20.27605
1997	18.74956
1998	22.01714
1999	15.82545
2000	16.21953
2001	14.53457
2002	13.94855
2003	12.59517
2004	14.61946
2005	7.94526
2006	7.23432
2007	6.18336
2008	4.7885
2009	6.00786
2010	8.91533
2011	8.91104
2012	7.56692
2013	8.92324
2014	7.78783
2015	10.48678