Year	% of total
1971	24.737534825221356
1972	24.298333620804897
1973	24.967678281340245
1974	27.35345787502654
1975	25.161510295920774
1976	24.584724521927793
1977	22.89099453249723
1978	19.524889127213452
1979	19.91814899442464
1980	20.671091812433325
1981	22.52466997045066
1982	23.506567949257708
1983	24.663396663835258
1984	23.98735139207477
1985	23.55391732521573
1986	22.952187872343806
1987	21.411113362651992
1988	21.43535104457724
1989	21.867864464721603
1990	21.39741596327737
1991	19.535991898850835
1992	18.623559364480926
1993	18.670468359449217
1994	18.436087310299555
1995	19.105653044043905
1996	17.575107596617503
1997	16.67852826515141
1998	17.124526324121923
1999	16.296352564746968
2000	16.267634259693757
2001	18.204850727258705
2002	16.87529353188504
2003	14.703463634491904
2004	15.565553537805979
2005	15.354498314739438
2006	14.932834699226877
2007	14.580635673942913
2008	16.44299822504726
2009	16.134015269918088
2010	16.331480107044804
2011	14.582428321718025
2012	17.060906193013825
2013	16.53165390475218
2014	18.135792920980453
2015	18.387555442826635