Year	% of total
1960	8.29555757026292
1961	7.924038104664109
1962	7.9240037071362375
1963	8.077978824715702
1964	7.353236831523924
1965	6.123009335529929
1966	7.280996302120968
1967	6.448938992042439
1968	6.8164794007490634
1969	10.187791616858828
1970	12.418743228602382
1971	16.250620523367136
1972	15.104580812445981
1973	14.319446241428388
1974	13.710522376889687
1975	13.010620330346665
1976	15.898260320376645
1977	15.023574796399487
1978	14.361546832284949
1979	11.95362838022738
1980	9.192307692307693
1981	7.953415707996022
1982	9.809399786906594
1983	8.150671876489088
1984	11.242589347862612
1985	11.350646975446939
1986	11.583327648543557
1987	11.39913057478667
1988	11.865251614779124
1989	13.298748855660666
1990	15.66252839987017
1991	14.880133915226878
1992	13.292216504135046
1993	13.217574117692863
1994	16.585749649786035
1995	16.151364674326725
1996	17.555157352447083
1997	15.203376133608693
1998	15.859416920050082
1999	15.505040389879163
2000	13.112536326285198
2001	14.321974225031523
2002	15.327974170592693
2003	19.216138526946313
2004	17.680958223025765
2005	20.204072138570563
2006	17.12904986674373
2007	15.712812376041255
2008	17.327093244897643
2009	18.612401230472283
2010	21.124915359024936
2011	19.973663926002054
2012	14.133313928103625
2013	10.302091402013943
2014	8.772072189041808
2015	12.601395657594352