  We have analyzed the Indices of Industrial Production (Seasonal Adjustment
Index) for a long period of 240 months (January 1988 to December 2007) to
develop a deeper understanding of the economic shocks. The angular frequencies
estimated using the Hilbert transformation, are almost identical for the 16
industrial sectors. Moreover, the partial phase locking was observed for the 16
sectors. These are the direct evidence of the synchronization in the Japanese
business cycle. We also showed that the information of the economic shock is
carried by the phase time-series. The common shock and individual shocks are
separated using phase time-series. The former dominates the economic shock in
all of 1992, 1998 and 2001. The obtained results suggest that the business
cycle may be described as a dynamics of the coupled limit-cycle oscillators
exposed to the common shocks and random individual shocks.
