| 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 | |
| 100 |
38.1 |
43.3 |
38 |
5.3 |
18.6 |
2.6 |
6.5 |
| 100 |
42.9 |
40.6 |
35.3 |
5.3 |
16.5 |
2.6 |
5.5 |
| 100 |
36 |
46.8 |
41 |
5.8 |
17.2 |
2.7 |
5.9 |
| 100 |
33.8 |
46.3 |
41.1 |
5.2 |
19.9 |
3.5 |
7.5 |
| 100 |
36.4 |
42.2 |
37.4 |
4.8 |
21.4 |
3.9 |
8.3 |
| 100 |
32.3 |
44.2 |
40 |
4.2 |
23.5 |
4.4 |
9 |
| 100 |
32.4 |
43.9 |
39.7 |
4.2 |
23.7 |
4.8 |
8.8 |
| 100 |
29 |
46.5 |
41.8 |
4.7 |
24.5 |
4.8 |
9.5 |
| 100 |
27.2 |
46.2 |
41.3 |
4.9 |
26.6 |
5 |
9.8 |
| 100 |
26.4 |
46.6 |
41.4 |
5.2 |
27 |
4.9 |
9.7 |
| 100 |
25.6 |
46.3 |
41.2 |
5.1 |
28.1 |
4.7 |
10.7 |
| 100 |
25 |
45.8 |
41.1 |
4.7 |
29.2 |
5.1 |
10.5 |
| 100 |
25.1 |
45.4 |
40.5 |
4.9 |
29.5 |
5 |
10.2 |
| 100 |
22.7 |
45.7 |
40.5 |
5.2 |
31.6 |
5.6 |
11.8 |
| 100 |
19.2 |
47.9 |
42.6 |
5.3 |
32.9 |
5.9 |
12.8 |
| 100 |
16.6 |
51.4 |
45.8 |
5.6 |
32 |
5.8 |
12.5 |
| 100 |
16.6 |
52.1 |
46.4 |
5.7 |
31.3 |
5.5 |
12.6 |
| 100 |
15.9 |
52 |
46.3 |
5.7 |
32.1 |
5.8 |
13.4 |
| 100 |
14.7 |
53.1 |
47.4 |
5.7 |
32.2 |
5.7 |
13.7 |
| 100 |
13.7 |
54.1 |
48.6 |
5.5 |
32.2 |
6.2 |
13.3 |
| 100 |
12.7 |
54.3 |
49 |
5.3 |
33 |
6.5 |
13.3 |
| 100 |
11.8 |
54.1 |
49 |
5.1 |
34.1 |
6.8 |
13.3 |
| 100 |
11 |
52.7 |
47.7 |
5 |
36.3 |
7.1 |
13.7 |
| 100 |
9.9 |
51.7 |
46.5 |
5.2 |
38.4 |
7.5 |
13.5 |
| 100 |
8.9 |
51.1 |
45.9 |
5.2 |
40 |
7.7 |
13.3 |
| 100 |
7.7 |
52.6 |
46.6 |
6 |
39.7 |
7.5 |
12.3 |
| 100 |
7.2 |
53.8 |
47.9 |
5.9 |
39 |
7.4 |
11.9 | |
