Year	Percent
1960	13.57363
1961	14.78004
1962	11.67231
1963	15.12399
1964	14.98532
1965	11.03194
1966	13.15273
1967	15.65617
1968	15.04346
1969	16.85434
1970	16.09262
1971	15.89077
1972	14.75064
1973	15.23034
1974	18.47476
1975	20.52806
1976	17.05431
1977	18.51476
1978	16.23125
1982	3.16176
1983	2.7329
1984	4.8304
1985	7.30237
1986	8.13294
1987	9.12948
1988	7.0355
1989	8.03107
1990	6.75351
1991	6.54307
1992	7.46811
1993	9.7593
1994	16.63991
1995	13.19249
1996	20.25016
1997	19.48478
1998	16.93422
1999	13.6915
2000	23.2739
2001	40.25038
2002	60.15617
2003	52.12177
2004	24.28387
2005	20.70431
2006	22.19288
2007	22.3152
2008	21.87903
2009	30.23108
2010	34.47906
2011	28.47213
2012	31.10026
2013	29.25255
2014	33.75971
2015	28.35604
2016	26.15117
2017	21.38443