Year	% of total
1960	0.1712386358544635
1961	0.18191190811296828
1962	0.1875425045828495
1963	0.1994313169095931
1964	0.19540192563329267
1965	0.19579531311672407
1966	0.22279956249284658
1967	0.21677535980243884
1968	0.2247739686342292
1969	0.2247234105532757
1970	0.2811690903274559
1971	0.277001112063397
1972	0.27603778565634135
1973	0.29430792852833926
1974	0.2655542658613431
1975	0.29000979226648066
1976	0.29679887705921715
1977	0.30127226944149427
1978	0.2911141763634831
1979	0.3130998469550729
1980	0.36198410937967257
1981	0.3867096376612669
1982	0.5092980485094909
1983	0.5371388810992992
1984	0.5727032614173345
1985	0.6093431300362312
1986	0.6511502064858928
1987	0.6547551954427206
1988	0.6591550677656534
1989	1.4196358880033688
1990	1.716781840041311
1991	1.2805608317914874
1992	1.4002818655249438
1993	1.428886436680163
1994	1.4561366834359344
1995	1.431599844509569
1996	1.4320014265893697
1997	1.4902731545476657
1998	1.5200662670131113
1999	1.6020712947685756
2000	1.7006224023252698
2001	1.756302795658564
2002	1.955846524801395
2003	2.1185593196609482
2004	2.3777611930302833
2005	2.6342617568448583
2006	2.9377548723348887
2007	3.307303933387858
2008	3.7777989712567726
2009	4.418150219804273
2010	5.0170687593488905
2011	5.952991547396904
2012	6.844037557979451
2013	7.806852085821634
2014	8.656307209155024
2015	9.63853540673744