Year	Percent
1971	7.12484
1972	9.62727
1973	25.23068
1974	10.28895
1975	4.21373
1976	13.57028
1977	10.44613
1978	10.55996
1979	13.58771
1980	8.20954
1981	3.51034
1982	15.17969
1983	4.73692
1984	11.06497
1985	5.98737
1986	13.91658
1987	1.11312
1988	24.13261
1989	2.89174
1990	30.38491
1991	8.77775
1992	11.18825
1993	17.38976
1994	10.97043
1995	16.64938
1996	7.68237
1997	11.34484
1998	7.40528
1999	5.37006
2000	25.34294
2001	8.94262
2002	8.91493
2003	6.0055
2004	3.87129
2005	6.55682
2006	4.04116
2007	5.0143
2008	10.42558
2009	9.76992
2010	3.19718
2011	5.34095
2012	8.04852
2013	4.47868
2014	5.83947
2015	7.5549
2016	5.25883
2017	5.29706