Year	% of total
1960	0.6884057971014492
1961	0.7227323947310477
1962	0.9079312673519923
1963	1.1297906166491896
1964	1.115454090848786
1965	0.933525408950471
1966	0.8823657886690255
1967	0.7987005209892808
1968	0.7522178694113275
1969	0.7222321909205096
1970	0.9992368596775733
1971	1.0156695418682067
1972	0.9363303927087406
1973	1.1564628574403248
1974	1.547479390297124
1975	1.973271069789397
1976	2.277495360284031
1977	2.6415982120101167
1978	3.820407964558688
1979	4.282425172678435
1980	5.062595538012036
1981	5.231434364472636
1982	5.530639096978658
1983	6.04086712996577
1984	7.632539707304896
1985	8.41642263981637
1986	8.884117076766529
1987	9.139014396994284
1988	8.722958568912782
1989	9.048879036006722
1990	9.248723365307168
1991	9.620709440515167
1992	9.738566493955094
1993	10.055945965430853
1994	10.235966945844153
1995	10.382313542919022
1996	10.84739300135724
1997	11.425894598761488
1998	12.125006408839779
1999	12.451992040415478
2000	12.706397565408512
2001	12.994039654200337
2002	12.615765760540858
2003	13.42286441625952
2004	13.333141632744058
2005	13.330947669341416
2006	14.90109631509082
2007	15.500039058677714
2008	16.522402424932306
2009	16.768747014647527
2010	17.013892896685352
2011	18.85154491531716
2012	19.17427920014055
2013	19.095504798160047
2014	20.0190627305668
2015	19.425944138806603
2016	19.88379950315437