We argue that it is possible to explain much of the history of the world’s shipping markets since 1950 as the interaction of two balancing feedback loops: a capacity adjustment loop which creates a “20-year” wave, and a capacity utilization adjustment loop which generates a “4-year” cycle. We show how this insight has been used rather successfully since the early 1980s for practical forecasting of turning points in the shipping market 1 - 4 years ahead of time. The basic mechanisms in the shipping system create a strong “deterministic backbone” which is visible through the exogenous noise, and hence predictable with useful precision. Our experience leads to a number of questions concerning system dynamics best practice, for future research.