1983 ........ 26.94
1984 ........ 32.25
1985 ........ 28.63
1986 ........ 26.18
1987 ........ 27.75
1988 ........ 28.06
1989 ........ 33.17
1990 ........ 33.72
1991 ........ 33.66
1992 ........ 35.24
1993 ........ 40.07
1994 ........ 30.97
1995 ........ 35.90
1996 ........ 37.71
1997 ........ 31.61
1998 ........ 32.49
1999 ........ 39.14
2000 ........ 26.86
2001......... 35.07
2002 ........ 34.75
2003 ........ 32.12
2004 ........ 29.46
2005 ........ 26.55
2006 ........ 28.94