Seasonally adjusted figures of the clearing banks' net deposits and advances and other accounts were published in the June 1963 Bulletin, and covered the period 1959-63. The method of adjustment used was a version of the United States Bureau of the Census Method II-commonly known as Univac, which is a computer programme based on moving averages. The series have been continued in the Bulletin and in Financial Statistics, and were last revised in September 1964; since then the monthly estimates have been obtained by extrapolation. There are drawbacks, however, to the use of Univac in connection with the banking figures, and this note introduces a new method of adjustment which has recently been developed in the Bank to try to overcome some of these difficulties. Although the new method is believed to be an improvement on the old, it should nevertheless be emphasised that there is no perfect system of seasonal adjustment; whatever method is used can only, at best, provide a broad guide to seasonal movements, and there will always be considerable scope for error. An example of the difficulties which can occur arises in the coming financial year, when the timing of tax payments by companies will be affected by the transition to corporation tax. Seasonal adjustments, which are based essentially on past experience, take no account of changes of this kind.
Seasonal adjustment of the London clearing banks deposits and advances