Year	% of total
1971	18.463611859838274
1972	18.85441527446301
1973	17.276422764227643
1974	30.187144019528073
1975	27.203065134099617
1976	26.837606837606838
1977	26.837606837606838
1978	9.743589743589745
1979	11.904761904761903
1980	11.851851851851853
1981	11.851851851851853
1982	12.36111111111111
1983	26.181353767560665
1984	10.298507462686567
1985	13.027295285359802
1986	13.027295285359802
1987	13.456790123456791
1988	13.987730061349692
1989	13.30891330891331
1990	13.793103448275861
1991	17.34475374732334
1992	11.298838437170012
1993	6.315789473684211
1994	6.282722513089005
1995	6.25
1996	10.019455252918288
1997	23.647469458987782
1998	19.575113808801213
1999	33.03370786516854
2000	36.88581314878893
2001	37.91208791208791
2002	35.240793201133144
2003	37.794486215538846
2004	21.594982078853047
2005	20.35175879396985
2006	19.38898971566848
2007	22.3811004041032
2008	24.590952839268525
2009	34.656810982048576
2010	32.04257661956322
2011	29.09219607149177
2012	39.200515796260476
2013	41.97906523855891
2014	46.824894514767934
2015	46.82507169192954