Year	% of total
1960	57.179161372299866
1961	54.72109691492677
1962	50.17991494929669
1963	49.26536731634184
1964	48.40514829322887
1965	42.66595289079229
1966	41.60125588697017
1967	38.03763440860216
1968	35.91625883632409
1969	35.5601233299075
1970	35.081374321880645
1971	30.168005843681517
1972	28.797826579126106
1973	29.29089443996777
1974	29.794721407624632
1975	28.775100401606423
1976	27.983225314525356
1977	25.704479768786126
1978	24.231317450621052
1979	22.857778766970846
1980	22.978365889519008
1981	24.118038606611936
1982	21.994370727784478
1983	24.045723617064706
1984	22.044849866970733
1985	18.41574167507568
1986	15.24907896844466
1987	17.186311787072242
1988	19.491770141495813
1989	16.469399538106234
1990	20.479973106230393
1991	18.278235294117646
1992	15.110024600246003
1993	21.716737766624842
1994	18.954221581548598
1995	18.304917965545528
1996	14.322870588235293
1997	16.33146297627606
1998	16.12192392099488
1999	16.949177986764195
2000	15.028484745762713
2001	17.190507566204285
2002	14.15475934135529
2003	20.670738636363637
2004	25.056531791907517
2005	24.864100992410975
2006	22.273471291168757
2007	19.636406109613656
2008	21.99986616235089
2009	18.615996168582374
2010	16.679961451975586
2011	18.715594728171332
2012	20.11637613245861
2013	17.844141732283468
2014	17.325681031770994
2015	16.711677539608573
2016	14.536279666452856