| 1978 |
| 1979 |
| 1980 |
| 1981 |
| 1982 |
| 1983 |
| 1984 |
| 1985 |
| 1986 |
| 1987 |
| 1988 |
| 1989 |
| 1990 |
| 1991 |
| 1992 |
| 1993 |
| 1994 |
| 1995 |
| 1996 |
| 1997 |
| 1998 |
| 1999 |
| 2000 |
| 2001 |
| 2002 |
| 2003 |
| 2004 |
| 2005 | |
| 24.4 |
7.2 |
| 13.22 |
3.7 |
| 10.23 |
2.7 |
| 5.24 |
1.3 |
| 9.27 |
2.4 |
| 7.15 |
1.8 |
| 4.69 |
1.1 |
| 3.45 |
0.8 |
| 5.5 |
1.2 |
| 7.51 |
1.6 |
| 7.73 |
1.5 |
| 10.53 |
2.1 |
| 11.24 |
2.2 |
| 10.87 |
2 |
| 12.97 |
2.4 |
| 14.68 |
2.6 |
| 16.09 |
2.6 |
| 17.72 |
2.8 |
| 16.22 |
2.6 |
| 18.75 |
3 |
| 19.96 |
3.3 |
| 21.17 |
3.4 |
| 21.82 |
3.4 |
| 23.99 |
3.7 |
| 27.73 |
4 |
| 28.27 |
3.7 |
| 30.14 |
4.1 |
| 28.97 |
3.7 | |
