Year	% of total
1971	1.3867060000579785
1972	1.176664981237833
1973	1.320865623748533
1974	1.6622348772025932
1975	1.521435065689886
1976	1.595112791213524
1977	1.7966369101013842
1978	1.8934335383743406
1979	2.009263991945595
1980	2.067932005054205
1981	2.2318901835435927
1982	2.6631117699416325
1983	3.3457940893869913
1984	3.9900609963891074
1985	4.535757402471853
1986	4.6511164976867105
1987	5.888428026168377
1988	6.969145976211802
1989	8.111426137745262
1990	13.370234670271012
1991	14.821339631583436
1992	15.310427776978653
1993	13.219105297397613
1994	12.730044771366334
1995	15.859173151146654
1996	16.76280022079467
1997	17.509959565924323
1998	17.580157225496475
1999	17.67025662034422
2000	18.411913562360656
2001	18.905278396345203
2002	20.16789759319564
2003	21.274104135577748
2004	21.748636776027354
2005	20.758196290228362
2006	21.152066719189445
2007	19.677681551230577
2008	20.83996380956252
2009	23.61520961567268
2010	27.172814115242023
2011	25.517007012752202
2012	24.842197609449205
2013	25.30459659933275
2014	26.07018925122561
2015	27.14783893763225