Year	% of total
1971	16.70775036335284
1972	22.59975023580178
1973	27.002834690120007
1974	25.52786027905568
1975	27.921575485489804
1976	33.05150051592201
1977	29.560389723252456
1978	29.57784015459523
1979	32.06566170136301
1980	33.9904807732744
1981	31.841015480242945
1982	28.425733964498484
1983	26.528821659978437
1984	23.60564154959357
1985	17.931983798190743
1986	15.468761072569784
1987	14.858491573440638
1988	14.62510893149781
1989	13.445294145807143
1990	13.192234671721115
1991	12.934109667829174
1992	12.20602731630388
1993	12.681654364674099
1994	9.51566536268312
1995	9.506416803655583
1996	8.662002714082373
1997	8.185587936981362
1998	8.074850950558488
1999	6.586653134565279
2000	5.5363600109476945
2001	4.9349581767015716
2002	4.784382258593207
2003	4.282286983669882
2004	4.630446844612389
2005	3.70124546097521
2006	2.837811798577413
2007	2.127765460392132
2008	1.8170811490112804
2009	1.3973128943365842
2010	1.351828530762348
2011	1.3413575939609628
2012	0.9639405610604647
2013	0.7996310281469404
2014	0.7369956066047508
2015	0.5861482375495422