Re: [Gretl-users] glitch with X-12

Allin Thanks. The new system should produce reasonable seasonal adjusment in a large number of cases. In Peter's case the problem is that the data may need some farther examination. This is an X12arima rather than a gretl question. Something of the order of 30% of series may need further attention. For an unemployment series I would expect that the adjustment would be additive rather than multiplicative. One expects unemployment to rise of fall with the season by numbers of persons rather than by a percentage of the current numbers unemployed. I would not expect a trading day effect if the measurement was always taken on the same day of the week each month. (If the measurement was taken on the last day of the month one might get a trading day effect). My advice to Peter, for the cases which appear to have a trading day effect, would be to look at the detailed x12arima output. The results of the "trading day" regression are fairly close to the top of the output. Having looked at this he may decide to 1) proceed without trading day adjustment, or 2) use a trading day adjustment, or 3) investigate further using x12arima directly. Best regards John On 9 October 2010 01:09, Allin Cottrell <cottrell(a)wfu.edu&gt; wrote: -- John C Frain Economics Department Trinity College Dublin Dublin 2 Ireland www.tcd.ie/Economics/staff/frainj/home.html mailto:frainj@tcd.ie mailto:frainj@gmail.com