Year	% of total
1971	13.91536408692337
1972	17.616580310880828
1973	9.750753218296357
1974	14.208588957055216
1975	27.249190938511326
1976	29.77614820532613
1977	32.860480640854476
1978	33.81068308749821
1979	32.114670380687095
1980	43.85459381580405
1981	47.538691962056916
1982	67.98016924523463
1983	67.34138731098489
1984	68.094141355981
1985	72.77031847960043
1986	66.12341304989667
1987	65.95180190139288
1988	68.90147456502883
1989	64.9087028693384
1990	55.43107647345348
1991	90.12059369202227
1992	62.08469055374592
1993	37.664783427495294
1994	44.943426015261814
1995	46.50143314786714
1996	37.54268891069677
1997	41.00059871276755
1998	58.167689434365
1999	67.66848239168989
2000	67.0606069981128
2001	69.29064987317415
2002	78.01001045047028
2003	75.38063413898799
2004	72.3022105875509
2005	74.90739470434902
2006	68.59075346062554
2007	68.10452690090865
2008	64.32974550232855
2009	71.16092904389657
2010	65.37025022357047
2011	61.98200393337626
2012	63.777830979171654
2013	60.87370043619429
2014	66.251151366288
2015	63.5810830707618