Year	% of total
1971	0.015139250199033876
1972	0.019304551068170313
1973	0.024798223752365747
1974	0.02304076820312413
1975	0.042650643688348616
1976	0.03656029372233884
1977	0.037933825435374074
1978	0.058625005082339324
1979	0.07297053316260964
1980	0.26762268173797693
1981	0.6252330696920196
1982	1.4655856787234578
1983	1.675632500055755
1984	2.1274379997853132
1985	2.8383238499711703
1986	2.8202337044471983
1987	3.6489930794644074
1988	3.8387476254276915
1989	3.884111569468298
1990	3.506145539733091
1991	3.722107984884936
1992	4.147954051393862
1993	5.185892428190895
1994	6.505296153809334
1995	7.220160036441035
1996	7.7229518096770855
1997	8.798093354395768
1998	8.828273722022256
1999	8.993566321397434
2000	8.80088174253106
2001	8.688461047950117
2002	8.551310935120036
2003	8.400369649800785
2004	7.72074779416266
2005	7.463530725512539
2006	7.107827467166699
2007	6.88250623549542
2008	6.895573646568347
2009	7.571408928884191
2010	7.682518218506135
2011	6.661385343862807
2012	6.717186905805558
2013	6.530831095762907
2014	6.6701988153763505
2015	7.116109113809616