Note 7 — Part II

Warren M. Persons, in a footnote on page 35 of the January, 1919, Review of Economic Statistics, expresses the method of ascertaining percentage departure from the secular trend in mathematical symbols as follows: “Let the original series beginning with January be X1, X2, X3, ... Xn, the ordinates of secular trend be O1, O2, O3, ... On, and the adjusted indices of seasonal variation for twelve months be S1, S2, S3, ... S12 per cent, respectively. Then the items for secular trend and seasonal variation are:

X₁ − S₁O₁/O₁, X₂ − S₂O₂/O₂, X₃ − S₃O₃/O₃, ... X₃ − S₁O₁₃/O₁₃ etc.”