Year	% of total
1971	1.4704467565652586
1972	2.7822937879388356
1973	3.0027450970157137
1974	1.5166616382699991
1975	4.599801850175134
1976	5.858046936956264
1977	7.001406219384694
1978	9.684328220233084
1979	12.261098210316211
1980	16.296297914596234
1981	20.02077463317023
1982	20.557977037413014
1983	28.591888351621105
1984	26.10228842007573
1985	24.042587216104565
1986	19.5338184151112
1987	22.497649673940526
1988	20.517068065884178
1989	23.161555470876348
1990	25.02732830722912
1991	21.95141639664176
1992	21.22179568486608
1993	22.554559056976863
1994	25.989630266938292
1995	23.015365737709907
1996	25.064450743442045
1997	33.8405575637054
1998	34.528474830483034
1999	34.70112034307328
2000	32.794414289429106
2001	32.56461985653843
2002	37.090433716771095
2003	37.5722894135033
2004	40.86848067022315
2005	40.642020424873465
2006	40.434573660564446
2007	41.59571961265921
2008	39.21605312163911
2009	39.392521045608206
2010	44.039180664178716
2011	47.0757584741765
2012	46.7060757986035
2013	46.82545377982974
2014	48.291844090430665
2015	52.69188657797842