The World3 model is a detailed simulation of human population growth from 1900 into the future. It includes many environmental and demographic factors.

Use the sliders to experiment with the initial amount of non-renewable resources to see how these affect the simulation. Does increasing the amount of non-renewable resources (which could occur through the development of better exploration technologies) improve our future? Also, experiment with the start date of a more environmentally focused policy.

This model describes the whole process about government response and economic impact when the covid-19 outbreak in Burnie, Tasmania. When the reported cases increase to a certain level, the government realizes its high risk, then publishes a series of policies to protect the public, such as travel restriction, social distance and quarantine. The economic damage is also severe, especially for tourism and hostility industry and retail industry.

Clearly, in the beginning, the number of infected people and death cases increase sharply, but due to government policies and vaccination, it effectively reduces covid-19 cases. For economy, on one hand, the government health policies slow down the pace of growth, on the other hand, the government build vaccine confidence, which leads to more people getting vaccinated, and help the economy back to normal.

This paper aims at describing a case where system dynamics modeling was used to evaluate the effects of information and material supply lead-time variation on sales contributions margins and operating cash conversion cycle of a commodity export business.  An empirical dynamic model, loaded with econometric theory of price effect on competitive demand, was used to describe the input data.  The model simulation outputs proved themselves relevant in analyzing the complex interconnections of multiple variables affecting  the profitability in a commercial routine, supporting the decision process among sales managers.