Year	% of total
1971	0
1972	0
1973	0.43396226415094336
1974	1.1297091547921139
1975	1.1793097167835351
1976	1.2183317902533457
1977	1.1328192273101283
1978	1.0493068959466574
1979	1.6412982201820085
1980	1.3664466413786924
1981	1.3177139576527195
1982	1.6190285828502897
1983	1.6524787180771157
1984	1.638099620384217
1985	1.764724859929669
1986	3.494142112957358
1987	4.247995230860945
1988	4.217108736414775
1989	3.9717938915084323
1990	4.425183663250947
1991	5.390837675974177
1992	5.958724710982659
1993	6.059422287411644
1994	5.395871706166614
1995	5.569202879512374
1996	4.72569772529821
1997	4.17689097454819
1998	4.078901176057574
1999	3.789880423998747
2000	3.6946639115108786
2001	3.786193618333739
2002	3.622016212921763
2003	3.7097245329506348
2004	3.8390793954112876
2005	4.147658393415428
2006	3.5244102062823406
2007	3.7840405319822676
2008	2.9898074745186864
2009	2.968769840973431
2010	3.1269847606673515
2011	2.9162579149201817
2012	3.4104964391266424
2013	3.881597976631711
2014	4.643511025021891
2015	5.490168349735487