Asymmetry and duration of I_BD fluctuation periods based on MS(2)-AR-TVTP model

International dry bulk shipping market is a derived demand of the international trade, it's a typical cyclical market affected by the world economy. Based on the monthly data of I_BD（Baltic Dry Index） from November 1999 to December 2021, the model of Markov Switching Auto-Regression Time-Varying Transition Probabilities of two regimes is built to analyze the duration, transition point of inflection and asymmetry of I_BD fluctuation periods. The results show that the MS（2）-AR-TVTP model can fit the main characters of I_BD fluctuation periods effectively. The average duration of period is 33.7 months. The length of the period presents a tendency to shorten from September 2008.The conversion between high-tide and low-tide period becomes more frequent. The different stages in the period have asymmetry of distribution. The duration of high-tide period is longer than low-tide period and has a more reliable performance. The cyclical characterization results can provide a basis for decision-making in the dry bulk shipping industry, shipbuilding investment and market operations.