Year	% of total
1971	2.697674418604651
1972	3.766816143497758
1973	4.47227191413238
1974	4.570970328789094
1975	4.779411764705882
1976	5.279034690799397
1977	5.769230769230769
1978	5.833956619296933
1979	5.695746214852199
1980	6.056434962147281
1981	5.185961236249345
1982	5.121042830540038
1983	3.465804066543438
1984	1.7148014440433215
1985	2.1712412945514132
1986	1.8966908797417272
1987	2.272727272727273
1988	1.9443385436523064
1989	1.5884743258219431
1990	1.5202076381164256
1991	1.4391143911439115
1992	1.278772378516624
1993	1.059322033898305
1994	1.1764705882352942
1995	1.1490125673249552
1996	1.1375387797311272
1997	1.1508951406649617
1998	1.6414141414141417
1999	1.2440758293838863
2000	1.0919540229885056
2001	1.8921208698107879
2002	3.5757575757575757
2003	4.234527687296417
2004	4.622871046228711
2005	5.794205794205794
2006	11.18292205248727
2007	15.983215716193019
2008	15.349410315085372
2009	22.18571675600899
2010	19.71520596711307
2011	18.510386758993413
2012	18.455026455026456
2013	18.475499092558984
2014	18.48179453836151
2015	17.889908256880734