Year	% of total
1971	7.517899761336516
1972	6.976744186046512
1973	4.526748971193416
1974	5.343845816907578
1975	8.051628764597417
1976	6.451612903225806
1977	6.275187104202648
1978	6.413831567205801
1979	6.808762581409118
1980	7.159904534606206
1981	7.422802850356295
1982	6.852791878172589
1983	7.618080243778567
1984	9.118541033434651
1985	9.168704156479219
1986	8.710801393728223
1987	6.738544474393531
1988	5.516111414527581
1989	7.043815862451471
1990	3.580146460537022
1991	4.521902967498822
1992	2.175543885971493
1993	1.899235030335004
1994	1.8638743455497382
1995	1.6469377251672672
1996	1.689301093077178
1997	1.7585931254996003
1998	1.7592592592592593
1999	1.7551823271296716
2000	1.7408416590977898
2001	0.9014423076923076
2002	1.355638880876839
2003	1.63727959697733
2004	1.8567271719551062
2005	2.04796550794934
2006	2.221330121771712
2007	2.66844563042028
2008	3.730814639905549
2009	3.1832651205093225
2010	3.5185185185185186
2011	3.4814475492441592
2012	3.792064289301859
2013	2.905083896819434
2014	3.2977691561590685
2015	3.129548762736536