Year	% of total
1971	2.4928332464760503
1972	2.3056489714969377
1973	2.17190927740036
1974	1.8111264799357083
1975	1.5878484106896935
1976	1.5394307197717751
1977	1.3640519383691405
1978	1.2467299150256483
1979	1.336447659205652
1980	1.2365008347936095
1981	1.1247447642018202
1982	1.0252408005303546
1983	1.0410548714908912
1984	0.9076600255460717
1985	0.848687393095042
1986	0.8893199481676035
1987	0.9564907254814027
1988	0.8742578534465972
1989	0.7047898535026775
1990	0.8581172549429148
1991	0.8631256972306666
1992	0.8663308951735086
1993	0.8944514580642046
1994	1.1352427081155974
1995	1.3497570227509208
1996	1.1901717451904958
1997	1.4872974550877143
1998	1.2848145746303747
1999	1.7682304903132815
2000	2.016792306803587
2001	1.7808853576081272
2002	1.6002654317746254
2003	1.6817143304664446
2004	2.0284592685478855
2005	2.082271784910364
2006	2.2494994701960422
2007	2.5603409711103176
2008	2.7159341095317795
2009	2.8125540553728414
2010	1.9419178195682434
2011	2.2564805165296065
2012	2.8037959301438202
2013	3.122914997589583
2014	3.1933293352369407
2015	3.330766474678448