Year	% of total
1971	0.35489184642735416
1972	0.3134611783725206
1973	0.2870368176328292
1974	0.26131143039966553
1975	0.2684033193780382
1976	0.26518727304421985
1977	0.23980185788555758
1978	0.24433261605250725
1979	0.23380280772577672
1980	0.26097284946027677
1981	0.2453863858733816
1982	0.24859009051231992
1983	0.4367451694861234
1984	0.9829268719144484
1985	0.9529120945349523
1986	0.8200707360548222
1987	0.7790113677094521
1988	0.8324860893539694
1989	1.205012546254117
1990	1.1965159114459536
1991	1.3238245276538443
1992	1.3505738123751032
1993	1.1458999679465909
1994	1.0772741999117623
1995	0.9644397784844698
1996	0.9362838917973874
1997	0.9212858653993168
1998	0.7130302809596116
1999	0.4610111347297947
2000	0.5318744035237144
2001	0.5192984477517587
2002	0.5833237558488322
2003	0.7253022730335761
2004	0.8403841671170746
2005	1.010170255246504
2006	1.5674736869151935
2007	1.0180202946528605
2008	1.0871767139688213
2009	1.0825152053067564
2010	1.0927902687160407
2011	1.4897203737654705
2012	2.0474229023363972
2013	2.2951504107583243
2014	2.398826341528357
2015	2.8161960624096696