Fixing the model for the seasonal component: A new revision policy

One of the multiple decisions that statisticians have to face on the release of seasonal and calendar adjusted series, is the revision policy when new data are available. The INE used to apply the policy of Partial Concurrent Adjustment: ARIMA Parameters in JDemetra+, but huge revisions from the beginning of the series were occasionally observed. Analyzing this issue deeply, we realized that revisions were due to two main reasons: model changes because of lack of admissible decomposition, and especially, changes in the autoregressive roots assignment. In this paper, we present the new revision policy applied at the INE, which may be considered a compromise between the Partial Concurrent Adjustment: ARIMA Parameters policy and the Partial Concurrent Adjustment: Fixed Model, both implemented in JDemetra+. This new policy avoids model changes by: (i) fixing the last estimated model with admissible decomposition when a model change is triggered and (ii) adjusting root assignment parameters to make sure autoregressive roots remain in the same component. In doing so, we improve the estimation of the model parameters with the new data, while avoiding big revisions, as shown in the examples.

The Coherence of Public Reason

Theories of public reason face a dilemma. If their standard of reasonableness is low, the view will be unacceptably anarchic and self-refuting, while if it is high, the exclusion of unreasonable views will manifest unequal treatment. This paper shows how to avoid this dilemma by distinguishing two models of public reason. The coercion model is vulnerable to the worry about anarchy but not self-defeat, while the reasons model is vulnerable to self-defeat but not anarchy. The coercion model can avoid anarchy without idealizing heavily via aggregation of individual policies into packages. The reasons model can avoid self-refutation by making acceptance of public reason one of the conditions for counting as fully reasonable, which is a natural constraint if the justification of the principle is relational.