Year	% of total
1971	1.265188398583203
1972	1.1391783969491176
1973	1.2119404600897719
1974	1.2970845082182942
1975	1.4525568563244111
1976	1.54913608734148
1977	1.5274343592742494
1978	1.5377923608269388
1979	1.5867563608248232
1980	1.424638329040535
1981	1.501611869456328
1982	1.6597736633146363
1983	1.7756636157956232
1984	1.6281107886932398
1985	1.5631642808945283
1986	1.8280182285249567
1987	1.9966734507097992
1988	1.9448477054230389
1989	1.9353339142427757
1990	2.1940454276826307
1991	2.3623840804100245
1992	2.7835597060262853
1993	2.6368738517159795
1994	2.5411878000283963
1995	2.513442073353637
1996	2.4649827669525806
1997	2.382390070695254
1998	2.2172870041602453
1999	2.264686952964194
2000	2.2013714484997884
2001	2.516021677076162
2002	2.58655349246492
2003	2.6874094051285304
2004	2.728610055765456
2005	2.825591809480373
2006	2.756915688252749
2007	3.153076587109983
2008	3.134954543736253
2009	3.493752432151573
2010	4.199813286186248
2011	4.2836643476529295
2012	4.769243144108856
2013	5.371310721498441
2014	6.372776376834785
2015	7.634021767912034