| Year | March | June | September | December |
|---|---|---|---|---|
1981 |
14.5 | 15.6 | 16.0 | 17.1 |
1982 |
14.7 | 16.2 | 18.1 | 18.3 |
1983 |
23.5 | 22.4 | 21.3 | 20.4 |
1984 |
17.6 | 15.9 | 13.1 | 12.5 |
1985 |
8.5 | 6.7 | 6.5 | 5.2 |
1986 |
3.9 | 3.5 | 3.6 | 4.1 |
1987 |
4.7 | 6.1 | 5.5 | 6.3 |
1988 |
10.5 | 12.2 | 13.9 | 14.7 |
1989 |
13.6 | 13.4 | 13.7 | 12.8 |
1990 |
12.2 | 12.0 | 11.5 | 11.3 |
1991 |
11.5 | 11.1 | 10.9 | 11.2 |
1992 |
10.3 | 9.6 | 9.2 | 8.6 |
1993 |
8.1 | 7.8 | 7.2 | 6.9 |
1994 |
5.7 | 5.0 | 4.3 | 3.0 |
1995 |
1.6 | 0.6 | -0.1 | 0.1 |
1996 |
-0.3 | 0.1 | 0.7 | 0.4 |
1997 |
0.2 | 0.7 | 0.8 | 0.9 |
1998 |
2.2 | 2.6 | 2.2 | 2.5 |
1999 |
3.7 | 4.0 | 5.0 | 5.8 |
2000 |
7.6 | 8.0 | 8.5 | 8.5 |
2001 |
8.1 | 8.6 | 8.7 | 9.2 |