Impact of COVID-19 on Port Production and Operation Based on System Dynamics: A Case Study of Shanghai Port in China

Table 2

Equations in the model.

Type	Equation
L	Real GDP = INTEG (GDP increment-GDP decrement, initial)
L	Port throughput = INTEG (port throughput increment, initial)
L	Domestic trade cargo throughput = INTEG (domestic trade cargo throughput increment, initial)
L	Foreign trade cargo throughput = INTEG (foreign trade cargo throughput increment, initial)
L	Passenger transportation = INTEG (passenger transportation increment, initial)
L	Port throughput capacity = INTEG (port throughput capacity increment, initial)
L	Cargo transportation = INTEG (cargo transportation increment, initial)
R	GDP increment = real GDP real GDP growth rate + port throughput coefficient of port throughput impact on GDP
R	GDP decrement = coefficient of COVID-19’s impact on GDP real GDP
R	Port throughput increment = (domestic trade cargo throughput domestic trade growth rate coefficient of COVID-19’s impact on domestic trade cargo throughput + foreign trade cargo throughput foreign trade growth rate coefficient of COVID-19’s impact on foreign trade cargo throughput) impact coefficient of port throughput capacity on port throughput + waterway passenger transportation waterway passenger growth rate
R	Domestic trade cargo throughput increment = transportation, storage, and postal industry increment coefficient of transportation, storage, and postal industry on port throughput conversion into domestic trade + industrial output increment coefficient of industrial output conversion into domestic trade + social consumer goods retail increment coefficient of social consumer goods retail conversion into domestic trade
R	Foreign trade cargo throughput increment = total import and export increment coefficient of import and export conversion into foreign trade
R	Passenger transportation increment = passenger transportation passenger transportation growth rate - coefficient of COVID-19’s impact on passenger transportation passenger transportation
R	Port throughput capacity = fixed assets investment fixed assets conversion rate + port collection and distribution capacity increment coefficient of collection and distribution capacity conversion into port throughput capacity
R	Cargo transportation increment = cargo transportation cargo transportation growth rate-coefficient of COVID-19’s impact on cargo transportation cargo transportation
A	Conditional function form, for instance: coefficient of COVID-19’s impact on GDP = IF THEN ELSE(Time < 2019, 0, 0.039)
A	Multiply form, for instance: increment of port collection and distribution capacity = road collection and distribution capacity growth rate of road collection and distribution capacity + waterway collection and distribution capacity growth rate of waterway collection and distribution capacity + air collection and distribution capacity growth rate of air collection and distribution capacity + railway collection and distribution capacity growth rate of railway collection and distribution capacity
A	Product form, for instance: industrial output = industrial output to GDP ratio nominal GDP
A	Table function form, for instance: real GDP growth rate = ([(2011,0)-(2022,0.09)], (2011,0.075), (2012,0.079), (2013,0.071), (2014,0.07), (2015,0.068), (2016,0.069), (2017,0.066), (2018,0.06), (2019,0.056), (2020,0.056), (2021,0.055), (2022,0.054))