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Forecasters have frequently been concerned with designing seasonal adjustment procedures that satisfy particular theoretical criteria (e.g. orthogonality, idempotency, symmetry, Lovell). In evaluating the merits of a particular technique, Monte Carlo studies are often undertaken and the results are then compared to those derived from the Census Bureau's X—11 routine (Wallis, Stephenson, Grether). However, many practical questions have not been addressed, such as to what extent can seasonal routines affect parameter estimates, forecast values, and policy scenarios? The purpose of this article is to focus upon these questions. Data from a short‐term petroleum demand model is seasonally adjusted six different ways. The seasonally adjusted data is then used to estimate the demand relationships of the model using the same structural equation in each case. The results of these estimations provide illuminating information about how seasonality affects parameter values. For policy purposes, this information can be crucial as various policies can be predicated upon an estimated response to a particular variable (e.g. the price of gasoline). The question answered here is how sensitive are the expected policy results to the type of seasonal routine employed in making the estimations.

Natural convective heat transfer in the near critical region of pure fluids Abstract. Natural convective heat transfer to carbon dioxide near its critical point was investigated. For a vertical flat plate of constant temperature the boundary layer equations were solved with variable fluid properties. The numerical results were compared with experiments and it was shown that calculated heat transfer coefficients near the critical point depend not only on the physical properties, but also on variations of these properties. Especially the extreme property variations have to be considered, if the critical point is inside the thermal boundary layer. In the vicinity of the critical point the properties are changing in a very narrow temperature range. With increasing distance this range becomes more extended and the property variations less important. Therefore the influence of physical property variations on natural convective heat transfer depends also on the temperature difference between the wall and the bulk temperature. "