1998 165 vehicles 1997 411 vehicles 1996 928 vehicles 1995 1,604 vehicles 1992 842 vehicles 1991 6,072 vehicles 1990 4,060 vehicles 1989 6,448 vehicles 1988 7,933 vehicles 1987 11,831 vehicles 1986 14,342 vehicles 1985 11,286 vehicles 1984 16,599 vehicles 1983 20,949 vehicles 1982 18,527 vehicles 1981 11,437 vehicles 1980 5,587 vehicles