Year	Percent
1960	6.25
1961	6.89655
1962	7.37705
1963	6.01504
1964	5.36913
1965	5.76659
1966	6.76757
1967	6.85148
1968	8.18964
1969	8.28877
1970	4.53079
1971	7.60768
1972	3.1817
1973	5.31182
1974	4.0523
1975	7.58008
1976	9.08842
1977	11.19641
1978	14.03689
1979	14.91622
1980	13.88577
1981	17.00618
1982	14.4574
1983	22.8268
1984	18.37084
1985	13.86113
1986	11.64423
1987	22.61237
1988	15.03514
1989	16.46289
1990	14.53698
1991	14.40976
1992	10.6383
1993	11.54015
1994	6.97413
1995	6.36344
1996	8.20981
1997	6.09685
1998	6.77161
1999	5.88494
2000	2.78114
2001	4.46826
2002	3.94866
2003	7.86879
2004	10.3471
2005	22.37271
2006	21.95542
2007	23.60675
2008	26.66391
2009	23.24776
2010	30.51985
2011	27.58877
2012	28.37305
2013	28.74509
2014	27.81258
2015	16.57762
2016	16.87434