Currently, the National Development Council (NDC) traces and revises history data of leading, coincident, and lagging indicators every month for the following reasons: new data is added to each component every month, data is revised by original data release agencies, as well as seasonal adjustment, long-term trend, and other factors. In order for the latest information to accurately reflect economic situations, the time series of business cycle indicators are traced and revised every month. However, the overall trend shows no great variations. The reason for revisions is further described below:
(1) The component values revised by original release agencies: Limited by time lags between statistical survey and release, some components can only serve as preliminary statistical values, while some components are estimate values. Thus, values are revised to actual values every month in line with the original release agencies.
(2) Seasonal adjustment: Since every addition of monthly data will result in slight differences in estimated seasonal factors, in general, the entire seasonal adjusted series must be traced and revised every year or every six months to avoid errors. In order to better ensure timely grasp of the pulse of the economic cycle by all sides, the council adopts the monthly trace and revision approach.
(3) Compilation method: When compiling business cycle indicators, the council ought to first estimate the long-term trend of each component and deviate to trend. When estimating long-term trend, slight differences in long-term trend values may arise for every addition of monthly data. In order to better ensure timely grasp of the pulse of the economic cycle by all sides, the council also adopts the monthly trace and revision approach, which is the same approach the OECD adopts.