Year	% of total
1960	41.6321243523316
1961	39.60470352764573
1962	38.43351548269581
1963	36.08635373341256
1964	34.270853400115584
1965	30.89774187626216
1966	26.23128269889951
1967	24.27332993370729
1968	22.961755114141717
1969	21.840134494880022
1970	20.054241374114813
1971	18.68743047830923
1972	10.13584117032393
1973	10.144927536231883
1974	8.81195908733281
1975	9.713855421686747
1976	8.031599736668863
1977	8.643533123028392
1978	7.007921998781232
1979	5.405405405405405
1980	5.856937109937591
1981	5.871474803513639
1982	6.609808102345416
1983	3.695458593054318
1984	1.2861736334405145
1985	1.8273020422787531
1986	2.4632117722328855
1987	3.7403400309119004
1988	2.8153762858689766
1989	0.7631507222676479
1990	9.294826388888888
1991	3.1489473684210525
1992	2.7300846023688665
1993	0.9626968973747017
1994	0.7312333825701625
1995	7.378314199395771
1996	4.033263971462545
1997	6.475724828676858
1998	1.8287376623376623
1999	0.8752660367976131
2000	5.792674364896074
2001	5.163386346004655
2002	4.85279256288735
2003	4.7774746769123295
2004	4.756410088437603
2005	4.910259859370223
2006	5.045955431754875
2007	5.820481705712029
2008	5.9441029341029346
2009	6.744002234636872
2010	6.0826670620798735
2011	5.215468577728776
2012	5.9061527849629245
2013	6.192375371409706
2014	5.5005
2015	12.01532012833031
2016	8.443946297803091