Estimating Potential Output for Taiwan with Seasonally Unadjusted Data

推估臺灣未經季節調整之潛在產出

林金龍(Jin-Lung Lin)；陳馨蕙(Shin-Hui Chen)

潛在產出 ； 產出缺口 ； 非加速通貨膨脹失業率 ； 季節單根 ； 歐肯法則 ； 菲力浦曲線 ； Potential GDP ； Output gap ； NAIRU ； Seasonal unit root ； Okun's law ； Phillips curve

臺灣經濟預測與政策

43卷2期（2013 / 03 / 01）

23 - 49

英文

有效評估潛在產出與產出缺口一直是執行貨幣與財政政策的重要環節。過去文獻中用以估計潛在產出的方法大多假設在潛在產出與非加速通貨膨脹失業率（NAIRU）中存在一般單根（regular unit root）。然而，這樣的假並不適用於估計臺灣未經季節調整的潛在產出。有鑑於此，本文以Watson's（1986） decomposition與Apel and Jansson's（1999a）systemapproach為例，以季節單根取代一般單根，從而考量更多的季節波動於模型中。同時，為了驗證模型的可靠性（robustness）以及更為有效評估臺灣的潛在產出與NAIRU，我們亦嘗試對NAIRU與失業缺口（unemployment gap）作不同的模型設定。實證結果顯示在一般單根假設下，亦即模型未考量季節波動時，資料本身的季節波動嚴重干擾估計結果且無法提供有用的訊息；反之，當以季節單根取代一般單根後確實更能有效評估臺灣潛在產出與產出缺口，並提供更為攸關的訊息供臺灣政府執行政策之參考。

Measuring potential output and the output gap have long been an important task for conducting monetary and fiscal policies. There exist several methods for this purpose and a partial list includes the univariate detrending method, the multivariate filtering approach, and the structural VAR system approach. One common feature of all these methods is assuming the existence of a unit root for the unobserved potential GDP. While this assumption is appropriate for the cases of US and most European countries where macroeconomic data are seasonally adjusted, it does not fit the Taiwanese economy. Almost all of Taiwan's macroeconomic data are seasonally unadjusted, and the seasonal unit root as well as richer dynamics have to be embedded in the model. In this paper, we analyze the impact of seasonality on various potential output measures. To check robustness and investigate how sensitive the results are to further changes in the specification of the NAIRU and the unemployment gap, distinct classes of NAIRU and unemployment gap concept are implemented. Empirical analysis confirms the importance of seasonal behavior. Switching from a regular unit root to a seasonal unit root improves the efficiency of measuring potential GDP and output gap for Taiwan and provides more relevant information in conducting monetary and fiscal policies.

1. Lin, T. F. (2010), "The Effect of Global Financial Crisis on Taiwanese Potential Output," Working Paper, Council for Economic Planning and Development.
2. Cross, R., J. Darby, and J. Ireland (1997), “Uncertainties Surrounding Natural Rate Estimates in the G7,”Working Paper, University of Glasgow
3. Zivot, E., J. Wang, and S. J. Koopman (2003), "State Space Modeling in Macroeconomics and Finance Using SsfPack for S+FinMetrics," Working Paper, University of Washington
4. Apel, M.,Jansson, P.(1999).A Theory-Consistent Approach for Estimating Potential Output and the NAIRU.Economic Letters,64(3),271-275.
5. Apel, M.,Jansson, P.(1999).System Estimates of Potential Output and NAIRU.Empirical Economics,24(3),373-388.
6. Basistha, A.,Startz, R.(2008).Measuring the NAIRU with Reduced Uncertainty: A Multiple Indicator-Common Cycle Approach.The Review of Economics and Statistics,90(4),805-811.
7. Beveridge, S.,Nelson, C. R.(1981).A New Approach to Decomposition of Economic Series into Permanent and Transitory Components with Particular Attention toMeasurement of the Business Cycle.Journal of Monetary Economics,7(2),151-174.
8. Blanchard, O. J.,Quah, D.(1989).The Dynamic Effects of Aggregate Demand and Aggregate Supply.The American Economic Review,79(4),655-673.
9. Cerra, V.,Saxena, S. C.(2000).IMF Working PaperIMF Working Paper,未出版
10. Christiano, L. J.,Todd, R. M.(2002).The Conventional Treatment of Seasonality in Business Cycle Analysis: Does It Create Distortions?.Journal of Monetary Economics,49(2),335-364.
11. Cleveland, W. P.,Tiao, G. C.(1976).Decomposition of Seasonal Time Series: A Model for the Census X-11 Program.Journal of the American Statistical Association,71(355),581-587.
12. Denis, C.,Mcmorrow, K.,Roger, W.(2002).,European Commission.
13. Diewert, W. E.(1996).,University of British Columbia.
14. Durbin, J.,Koopman, S. J.(2001).Time Series Analysis by State Space Methods.Oxford:Oxford University Press.
15. Fabiani, S.,Mestre, R.(2001).ECB Working PaperECB Working Paper,未出版
16. Fok, D.,Franses, P. H.,Paap, R.(2005).,Erasmus University Rotterdam.
17. Gerlach, S.,Yiu, M. S.(2004).Estimating Output Gaps in Asia: A Cross-Country Study.Journal of Monetary Economics,18(1),115-136.
18. Ghysels, E.,Granger, C. W.,Siklos, P.(1996).Is Seasonal Adjustment a Linear or Nonlinear Data Filtering Process?.Journal of Business and Economic Statistics,14(3),374-386.
19. Hjelm, G.,Jonsson, K.(2010).,National Institute of Economic Research.
20. Hodrick, R. J.,Prescott, E. C.(1997).Postwar U.S. Business Cycles: An Empirical Investigation.Journal of Money, Credit and Banking,29(1),1-16.
21. Koopman, S. J.,Ooms, M.(2006).Forecasting Daily Time Series Using Peri-odic Unobserved Components Time Series Models.Computational Statistics and Data Analysis,51(2),885-903.
22. Koopman, S. J.,Shephard, N.,Doornik, J. A.(1999).Statistical Algorithms for Models in State Space Using SsfPack 2.2.Econometrics Journal,2(1),107-160.
23. Kuttner, K. N.(1994).Estimating Potential Output as a Latent Variable.Journal of Business and Economic Statistics,12(3),361-368.
24. Laubach, T.(2001).Measuring the NAIRU: Evidence fromSeven Economies.Review of Economics and Statistics,83(2),218-231.
25. Matas-Mir, A.,Osborn, D. R.(2004).ECB Working PaperECB Working Paper,未出版
26. Matas-Mir, A.,Osborn, D. R.,Lombardi, M. J.(2008).The Effect of Seasonal Adjustment on the Properties of Business Cycle Regimes.Journal of Applied Econometrics,23(2),257-278.
27. Richardson, P.,Boone, L.,Giorno, C.,Meacci, M.,Rae, D.,Turner, D.(2000).OECD Working PapersOECD Working Papers,未出版
28. Staiger, D.,Stock, J. H.,Watson, M. W.(1996).NBER Working PaperNBER Working Paper,未出版
29. Stephanides, G.(2006).Measuring the NAIRU: Evidence from the European Union, USA and Japan.International Research Journal of Finance and Economics,1(3),29-35.
30. Tsay, R. S.(2005).Analysis of Financial Time Series.Hoboken, NJ:Wiley-Interscience.
31. Watson, M.W.(1986).Univariate Detrending Methods with Stochastic Trends.Journal of Monetary Economics,18(1),49-75.
32. Wu, C. S.、Lin, J. L.(2002)。Estimating Potential GDP for Taiwan and Its Application to Policies。Industry of Free China，92(10)，1-34。

1. (2016)。台灣產出缺口估計方法之評估。中央銀行季刊，38(3)，3-46。
2. (2017)。應用勞動市場流動率探討台灣自然失業率。中央銀行季刊，39(2)，1-32。