Year Cases per 100,000 1983 26.64 1984 25.09 1985 24.97 1986 27.46 1987 26.14 1988 27.75 1989 28.76 1990 26.65 1991 28.37 1992 29.06 1993 27.81 1994 29.77 1995 29.43 1996 27.55 1997 27.96