Year	Percent
1960	18.91612
1961	9.85781
1962	7.74946
1963	31.79653
1964	33.50286
1965	25.92306
1966	31.11946
1967	15.55094
1968	14.51582
1969	13.18203
1970	15.45996
1971	12.1388
1972	11.2511
1973	13.44158
1974	16.18111
1975	9.96313
1976	12.15318
1977	10.32819
1978	12.34875
1979	12.6488
1980	16.47847
1981	14.1409
1982	12.14959
1983	16.23824
1984	26.01301
1985	27.51107
1986	24.71098
1987	25.98136
1988	25.499
1989	25.48974
1990	29.5038
1991	20
1992	16.38418
1993	11.32987
1994	22.62529
1995	28.48229
1996	30.00276
1997	18.75
1998	29.79009
1999	23.63567
2000	11.44961
2001	11.98768
2002	15.67134
2003	24.00044
2004	22.72951
2005	22.94418
2006	21.7001
2007	39.07191
2008	39.0278
2009	26.81379
2010	41.11115
2011	39.51562
2012	30.80301
2013	36.44586
2014	36.83219
2015	27.72557
2016	27.21898
2017	35.60336