Year % of total 1960 0 1961 0 1962 0 1963 0 1964 0 1965 0 1966 0 1967 2.001187144916476 1968 1.4689265536723164 1969 4.055488174651304 1970 3.3111635557462633 1971 2.0157643106344487 1972 3.7756202804746493 1973 6.108682747827964 1974 9.018483110261313 1975 4.366854697529663 1976 5.895786726323639 1977 3.014062571572534 1978 0.7334413246940245 1979 0.2717145186124445 1980 0.17259691980881572 1981 0.1576211979211042 1982 0.3524229074889868 1983 0.6265806061978636 1984 0.22960020408907028 1985 0.3426633963353051 1986 0.09798432250839866 1987 0.051509220150406924 1988 0.04349280695884911 1989 0.015944894444798775 1990 0.03099333643266698 1991 0.07508409418548774 1992 0.6110536876026024 1993 0.1838074398249453 1994 0.06025652061633813 1995 0.14142310465309743 1996 0.04386806678913169 1997 0 1998 0.0026587259385302564 1999 0 2000 0 2001 0 2002 0 2003 0.04904725703215048 2004 0.05605381165919283 2005 0.00930925339787749 2006 0.0527498738589973 2007 0.0022855575617671932 2008 0.30101936101799276 2009 0.020712033691574806 2010 0.004453946196329948 2011 0.0044960996335678795 2012 0.0067775167178745705 2013 0.006933530553757974 2014 0.006895759108148489 2015 0.00226218753534668