The National Development Council uses six series, as the components of reference series, namely, gross domestic product, industrial production index, nonagricultural employment, index of producer’s shipment for manufacturing, sales of trade and food services, and real customs-cleared exports. Through seasonal adjustment, de-trending, and other processing and by eliminating interferences from irregular factors, the above series are combined into reference series using the same weights. The identification of turning points is based on Bry-Boschan routine.
1. Turns over 6 months of the beginning and end of a series.
2. Cycle duration minimum 15 months.
3. Phase duration minimum 5 months.
4. If flat turning point or double turning points in zone, select last turning point.
5. Extreme values ignored.