Year	% of total
1971	8.169965740388276
1972	9.204795473934713
1973	11.017489524503553
1974	16.65351223362273
1975	15.287078495859255
1976	18.6110210112805
1977	21.289128239649948
1978	26.13044582751175
1979	23.42436974789916
1980	22.491746806372902
1981	19.758195391106785
1982	18.863540868533576
1983	18.195460513974865
1984	18.63583452722063
1985	18.81725595695619
1986	17.87422285987566
1987	14.94950889057576
1988	2.7231736300837386
1989	4.128316188413644
1990	2.918772691677938
1991	3.3086975674220547
1992	3.4063465318730697
1993	4.326657367686923
1994	4.264023286916844
1995	3.453061810524301
1996	3.1252926303961046
1997	2.1726379015039536
1998	2.1816165658221442
1999	2.43825455693206
2000	1.626236284013187
2001	1.3299949464786143
2002	1.968270530484479
2003	1.864014364014364
2004	1.9842610920677837
2005	1.378149731647412
2006	0.8329304206408509
2007	1.3228683885692993
2008	0.6212991207608111
2009	0.7739317146834667
2010	0.8540322054892756
2011	0.2738740179517422
2012	0.4723158504905644
2013	0.5247393717058674
2014	0.44963453875167814
2015	0.373394608345985