Year	% of total
1960	31.561016343708793
1961	30.890023869228916
1962	29.49478329387069
1963	28.60054272007523
1964	27.144098953191627
1965	27.91323306515976
1966	27.336516761627383
1967	26.400871483563105
1968	24.851856556308714
1969	23.88273780621962
1970	22.48599398839159
1971	22.846460936986535
1972	22.098527479106103
1973	20.498630548526087
1974	22.425578103603154
1975	22.0671657095845
1976	19.88617224494424
1977	19.24636883629735
1978	19.71373810376419
1979	19.9078692702718
1980	19.323567176533235
1981	19.437794070589305
1982	20.113688166788275
1983	20.267928950896607
1984	19.365061518537193
1985	18.55992571538071
1986	18.200850668240918
1987	17.31385935558122
1988	16.84427577519348
1989	15.532563415821905
1990	15.69651125913879
1991	15.76301776735466
1992	15.495373125912378
1993	16.118367601336136
1994	15.180123732419181
1995	15.74830093187197
1996	15.745050416269054
1997	15.481074765940614
1998	14.671901231760087
1999	14.372232397652281
2000	14.034293445260465
2001	13.17449720351441
2002	13.287169475124072
2003	12.91496427131254
2004	12.94503332842664
2005	12.699975230077373
2006	12.831046660390749
2007	12.288842031200026
2008	12.766016164258541
2009	13.11202687407281
2010	12.790283590781309
2011	13.244265044330705
2012	13.266595564964941
2013	13.475656872595343
2014	13.38503415712507
2015	13.10457851426069