Annual % of total
1960 0
1961 0
1962 0.0038635397751419854
1963 0.007259264636492323
1964 0.0067297015377368
1965 0.006062810719049351
1966 0.0060947737315252175
1967 0.005673597912115968
1968 0.008171714970581825
1969 0.3428365211115121
1970 1.8680445151033385
1971 2.6859008208919395
1972 3.713879898479521
1973 3.7958395882479095
1974 4.476405259350666
1975 4.761904761904762
1976 5.318096681187785
1977 5.889474711970318
1978 6.837901615538209
1979 7.460257854550006
1980 8.011894082859895
1981 8.845908946195479
1982 9.631137912130944
1983 10.137062207663098
1984 10.173589584624922
1985 12.507600632372611
1986 11.716254832745
1987 11.321430105525408
1988 11.376816681878818
1989 10.933477669672207
1990 12.851193474962063
1991 11.98275471270447
1992 12.240641675361454
1993 12.549606036128655
1994 12.815485341084438
1995 13.267990380955677
1996 12.849616475850329
1997 12.637325683737
1998 12.312865165110177
1999 12.625957542637522
2000 13.030020660547208
2001 13.485494550092763
2002 13.923356570035988
2003 13.348467570101425
2004 12.8892635584636
2005 11.759884712186409
2006 14.118135764944276
2007 15.750106131769467
2008 16.85687335907336
2009 17.007749335358906
2010 16.81603743384536
2011 17.763234310599582
2012 16.960956269279624
2013 18.275538270888813
2014 19.629771817886883
2015 19.631719552091923
2016 20.607057766434004