Year	% of total
1960	6.80317064678099
1961	7.419572723308389
1962	7.866223036967512
1963	8.288001561275824
1964	10.055652078171462
1965	10.546523310320506
1966	11.291141410145556
1967	12.349742287745592
1968	13.384532438723573
1969	16.178622129998175
1970	18.809575273409543
1971	21.449137903513833
1972	23.60248615075087
1973	25.1446913801601
1974	23.592010719995688
1975	22.070167146665863
1976	22.758368033177305
1977	22.192883335621936
1978	21.84922900923947
1979	19.694426257198693
1980	17.308789725082175
1981	15.437664484986522
1982	13.357526488609489
1983	12.11734444393439
1984	10.893036547319978
1985	8.975018315368231
1986	9.125549370234182
1987	8.70113752427743
1988	9.137818618140372
1989	9.703085107753399
1990	8.328397522556712
1991	8.326522882294828
1992	8.328160339826205
1993	7.751134841491994
1994	7.822301323907828
1995	7.125034536254689
1996	6.831897564774893
1997	6.790727309501296
1998	6.9335215349660615
1999	6.508078092281452
2000	6.046885857291897
2001	5.996216489235307
2002	5.674440555645397
2003	5.888748939137076
2004	5.332750699204335
2005	5.103988014031207
2006	4.032219170666383
2007	4.01895569781785
2008	3.5320383797307078
2009	3.0516891528556553
2010	2.6950204623188956
2011	2.8333019787774796
2012	3.1451922947446755
2013	2.688266089094644
2014	2.3226294680019173
2015	2.1656925710841204