Year Number 1961 11600 1962 12100 1963 12600 1964 13100 1965 13600 1966 14100 1967 14600 1968 15100 1969 15600 1970 16150 1971 16500 1972 17150 1973 17450 1974 17750 1975 18062 1976 18397 1977 21167 1978 22768 1979 24347 1980 24105 1981 24534 1982 24610 1983 23722 1984 29659 1985 31620 1986 30768 1987 22578 1988 22405 1989 22127 1990 25086 1991 35375 1992 37627 1993 45776 1994 89106 1995 97817 1996 109501 1997 115487 1998 122958 1999 145850 2000 162746