Year	Percent
1960	6.96136
1961	5.83551
1962	5.0445
1963	6.75823
1964	7.0702
1965	6.50063
1966	8.53281
1967	9.26474
1968	10.31932
1969	10.78345
1970	9.91272
1971	11.21947
1972	8.81976
1973	9.09738
1974	8.66018
1975	8.13716
1976	8.13473
1977	8.07826
1978	9.58657
1979	16.09393
1980	14.96243
1981	11.47825
1982	8.48574
1983	8.36516
1984	8.6195
1985	8.54617
1986	9.03949
1987	10.10653
1988	13.29438
1989	13.38945
1990	16.97191
1991	8.24324
1992	11.20868
1993	11.44758
1994	10.90313
1995	10.9424
1996	11.637
1997	12.81397
1998	14.7814
1999	14.92043
2000	15.04496
2001	18.4997
2002	14.26293
2003	17.89299
2004	23.3786
2005	22.19498
2006	25.29129
2007	29.60807
2008	40.31782
2009	34.76421
2010	20.7749
2011	17.60921
2012	17.56091
2013	15.86062
2014	15.5797
2015	13.05677
2016	14.79277
2017	15.15052