Year Years 1960 1.304 1961 1.5 1962 1.43 1963 1.127 1964 1.234 1965 1.033 1966 1.23 1967 1.561 1968 1.858 1969 1.942 1970 2.143 1971 2.369 1972 2.539 1973 2.893 1974 2.78 1975 2.994 1976 3.104 1977 3.12 1978 3.533 1979 3.481 1980 3.351 1981 2.896 1982 2.333 1983 1.842 1984 1.712 1985 1.73 1986 1.747 1987 1.847 1988 1.4 1989 1.217 1990 1.216 1991 1.256 1992 1.492 1993 1.711 1994 1.806 1995 2.002 1996 1.953 1997 1.899 1998 1.656 1999 1.272 2000 1.114 2001 0.9871 2002 0.9046 2003 0.8571