No abstract

A simple modification of the well-known mixed Poisson model for library circulations is proposed which takes account of the periods when a book is out on loan, and hence, unavailable for borrowing. It is found that this helps to explain the rapid tailing-off in the upper end of observed frequency-of-circulation distributions.Practical consequences of the model include the possibility of investigation of the effects of proposed changes in loan policy and more reliable prediction of future use to assist in, for example, decisions concerning relegation of stock to storage.