Vertical integration and capacity investment in a two-port system

We model the vertical investment of a container shipping line in the port capacity in a two-port system. Our analytical and numerical analyss suggests that the relative scale of the capacity investment depend on the initial port capacity and the relationship between the ports. When a port has a sufficiently large initial capacity and the ports do not have highly complementary operations, a vertical investment leads to higher investments. Moreover, the investment of a shipping line in a port always increases its own profit and reduces the competitor’s profit. However, when compared with port self-investment, vertical investment always reduces the local social welfare.