Year	Percent
1971	11.40773
1972	13.16057
1973	11.90088
1974	8.23937
1975	9.92273
1976	10.78488
1977	9.45471
1978	8.95657
1979	11.41767
1980	9.96014
1981	8.52087
1982	7.17946
1983	7.43464
1984	8.3116
1985	7.30378
1986	5.94965
1987	6.09554
1988	6.51012
1989	6.76845
1990	5.98868
1991	6.88852
1992	6.7173
1993	7.32604
1994	6.50773
1995	6.45081
1996	6.43713
1997	6.07737
1998	5.94612
1999	6.27578
2000	7.7529
2001	7.98138
2002	5.85289
2003	5.72933
2004	5.36559
2005	4.5177
2006	4.98361
2007	6.06837
2008	5.01251
2009	5.75069
2010	6.58792
2011	6.28424
2012	5.51752
2013	7.03372
2014	4.77686
2015	4.47129
2016	5.55164
2017	5.91485
2018	5.66435
2019	5.68749
2020	5.65201