T HE methods followed in the original construction of our index of business conditions were fully set forth in this REVIEW for April I919; and such changes as have been found necessary since I919 have been explained, as occasion offered, in subsequent numbers. Our methods of interpreting the index have never been presented so exhaustively', because in part they have developed out of our experience in handling current data and have been presented only in our Weekly Letters as occasion required. It has therefore happened that our interpretation of the index has not always been fully understood; and misunderstanding is easy unless any particular passage is interpreted not only with reference to its immediate context but also with reference to what has gone before. present article is devoted partly to various matters concerning which we sometimes receive inquiries, and partly to certain criticisms which have been offered recently, particularly those of Mr. Karl G. Karsten in his paper on The Harvard Business Indexes -A New Interpretation in the Journal of the American Statistical Association for December I926.