Year	% of total
1960	72.12772797481357
1961	69.75669076459042
1962	69.21717560361763
1963	69.71001924883554
1964	68.1674166149277
1965	69.59110062973795
1966	68.76136156104687
1967	66.24079800331194
1968	65.51641274571057
1969	57.043839001919274
1970	54.346032039575576
1971	53.1285150843177
1972	50.17854951994119
1973	51.613895168549675
1974	51.93912149896559
1975	47.66505956526852
1976	45.07610232482532
1977	45.55306905628098
1978	44.445323546576525
1979	42.55074363711407
1980	39.59806602427958
1981	33.82147341478727
1982	29.8067730937455
1983	28.457697898724852
1984	30.653190835902876
1985	29.266406955060248
1986	31.010731967898714
1987	31.873471006187927
1988	30.3177079391172
1989	30.161399872283106
1990	28.639913794964357
1991	27.838666068833923
1992	29.7638545885607
1993	30.045656181786345
1994	29.982114220599737
1995	29.289170954562042
1996	30.736419072580258
1997	29.75087974082556
1998	28.025357081133293
1999	24.467962464225263
2000	22.622225912864995
2001	22.891121892831496
2002	23.085975813297114
2003	22.873787595210082
2004	24.0894510485188
2005	23.659011958993165
2006	19.713460115676867
2007	16.151274105087932
2008	13.167049866738841
2009	12.170354326513015
2010	11.51979150601258
2011	10.254952587195088
2012	10.330714298599672
2013	10.40420686553414
2014	10.928487267979623
2015	11.288868750735006