Year January December     d
1  1959  315.42   315.43 minus
2  1960  316.27   316.03  plus
3  1961  316.73   316.85 minus
4  1962  317.78   317.53  plus
5  1963  318.58   318.20  plus
6  1964  319.41   318.55  plus
7  1965  319.27   319.25  plus
8  1966  320.46   320.87 minus
9  1967  322.17   321.80  plus
10 1968  322.40   322.74 minus
11 1969  323.83   323.95 minus
12 1970  324.89   324.96 minus
13 1971  326.01   325.85  plus
14 1972  326.60   327.39 minus
15 1973  328.37   328.48 minus
16 1974  329.18   329.41 minus
17 1975  330.23   330.59 minus
18 1976  331.58   331.52  plus
19 1977  332.75   333.68 minus
20 1978  334.80   334.78  plus
21 1979  336.05   336.56 minus
22 1980  337.84   338.04 minus
23 1981  339.06   339.44 minus
24 1982  340.57   340.32  plus
25 1983  341.20   342.82 minus
26 1984  343.52   344.04 minus
27 1985  344.79   345.38 minus
28 1986  346.11   346.72 minus
29 1987  347.84   348.78 minus
30 1988  350.25   351.18 minus
31 1989  352.60   352.37  plus
32 1990  353.50   354.07 minus
33 1991  354.59   354.89 minus
34 1992  355.88   355.33  plus
35 1993  356.63   356.78 minus
36 1994  358.34   359.05 minus
37 1995  359.98   360.74 minus
38 1996  362.09   362.38 minus
39 1997  363.23   364.34 minus