Annual % of total
1960 0.025731140956445336
1961 0.025528470471031413
1962 0.036462292427585266
1963 0.047976485449157065
1964 0.08438818565400844
1965 0.2709229047647093
1966 0.2667710037703635
1967 0.46911456173683785
1968 1.0330952985101678
1969 1.949956557486982
1970 3.540866518428677
1971 5.6375853822294
1972 8.126936735201648
1973 8.642002744551176
1974 11.045403537521599
1975 11.83488746469034
1976 12.372263891014848
1977 13.075747653350797
1978 13.48419470571124
1979 13.841946049219853
1980 15.27656449795536
1981 15.990898212989663
1982 17.025998943730237
1983 17.81958676297665
1984 18.83326059396887
1985 19.29601634855968
1986 19.050719825668736
1987 18.81500480923373
1988 18.572705008131543
1989 18.01471283496284
1990 19.42023280461298
1991 20.43165936108286
1992 21.0047786538392
1993 24.482170687486125
1994 25.760573974112333
1995 28.44689465753686
1996 31.942339808320785
1997 33.420928340321254
1998 34.627073881492485
1999 36.91710621027644
2000 37.76016675469705
2001 36.448422898912725
2002 37.08495200196141
2003 36.28576593860685
2004 37.05947337365393
2005 36.21145541990381
2006 34.27741858060705
2007 35.47598665809963
2008 37.7998759744173
2009 38.458876633986925
2010 40.32033147221819
2011 36.25166396651815
2012 32.55220112186349
2013 33.25520438793979
2014 33.0918353621791
2015 35.297977620700856
2016 41.9543358230621