It is designed to be 'sustainable', in the sense that a run should and could continue forever, across many hundreds of generations of agents, if allowed. The PMM exists in both the C++ version of ModEco, and in this NetLogo version, slightly modified. This version of ModEco, written using the NetLogo ADE, is in many ways more simple, but it was still, nevertheless, very difficult to create a stable dual biophysical/economic model. This version of ModEco was written using that ODD description, and is, itself, also described using the ODD protocol (which can be downloaded from the NetLogo Modeling Commons with this model), since it is in fact slightly different. It is described using the ODD protocol, a protocol of which the purpose is to enable people to recreate the model on a different platform. One of the many economic models that could be constructed there was called the PMM, and it has now been dubbed the PMM #1. The original ModEco Application was written in C++ and can be downloaded from the OpenABM website at. Even so, sustainability has been difficult to achieve. There is only one species sharing the universe of ModEco, and the conservation of biodiversity, or the conservation of renewable sources of natural capital are not modelled.

Depth completeness - this third dimension of completeness is not modelled here.

Longitudinal completeness - there is a cradle-to-grave life-cycle for living agents, and a harvest-to-waste life-cycle for economic goods and.

Vertical completeness - there is a biophysical economy capped by a social (or monetary) economy, and they co-evolve.

So, what do I mean by 'complete'? A ModEco economy is an abstraction of an economy that is complete in (only) two out of three ways: To my knowledge, it is the only example of such a complete model economy, as of this date (June 18th, 2014). ModEco is NOT intended to be a SIMULATION of any real economy, but, rather, a DEMONSTRATION of the dynamics of an extremely simple but complete economy. When I talk about ModEco in the following material, it is applicable to both this version (written in NetLogo) and to a larger ModEco application (written in C++) as well. The answers have proven to be very elusive. These seem like simple questions that could and should be addressed in a first-year economics course.

Where, exactly, does economic profit come from?.

What is the impact of the laws of conservation of mass and energy on long-term economic dynamics?.

What are the minimum essential characteristics (the necessary and sufficient characteristics) of a truly multi-generational sustainable economy in a biophysical world?.

ModEco is being written as part of a personal study of the dynamics of sustainability. A variety of emergent phenomena become apparent as a run proceeds, including a distinctive type of spatial distribution and a distinctive distribution of wealth among the agents. In the economic system, all exchanges of mass and energy (or goods and services) are reciprocated by exchanges of cash, which flows in a direction counter to the physical flows.

Mass and energy are conserved in every event, as well as at an overall level.

In the biophysical subsystem, many generations of agents are born, live, work, eat, reproduce and die in a world that obeys the laws of conservation of mass and energy - a world in which the carrying capacity is real and 50% of all agents die of hunger or old age, being too unhealthy to reproduce.

The PMM demonstrates a multi-generational sustainable economy having a biophysical subsystem which co-evolves with an economic subsystem. This model environment is called ModEco (NetLogo ADE), and the configurations that are sustainable are called PMM #2, which is short for The Perpetual Motion Machine, second implementation. Do you have questions or comments about this model?

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