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## NetLogo User Community Models

## WHAT IS IT?

This simple model demonstrates Kenneth Waltz's theory of nuclear proliferation ("The Spread of Nuclear Weapons") where, on a long enough timeline, systemic forces in the international system will compel states to build their own nuclear weapons programs.

## HOW IT WORKS

Given that at least one state has nuclear weapons (illustrated with the rocket), other states in adversary relationships with the nuclear state will proliferate according to a user-defined probability. As long as the probability is greater than 0%, all states will proliferate eventually.

## HOW TO USE IT

Choose a number of states between 1 and 200 to represent the international system of states or a region of states. Pick a number of states between 1 and 100 that initially have nuclear weapons. Decide upon the average node degree between 1 and 6. This number is the average number of adversaries to a given state. A state with 3 nodes, for example, is in adversarial relationships with three states. Finally, designate a probability that a state will proliferate given their observation that an adversarial neighbor has nuclear weapons. This model can be run once ("go") to see what happens at each round, or it can be run forever (go-forever) to identify the number of rounds necessary before every state has proliferated. The simulation will automatically end once everyone has nuclear weapons.

## THINGS TO NOTICE

How does increasing the average node degree decrease the time necessary for the simulation to end?

## THINGS TO TRY

See above.

## EXTENDING THE MODEL

Because Waltz's theory does not represent the world we live in (after seven decades of nuclear weapons, only ten states have proliferated, and only nine states presently have nuclear weapons), this model will be extended to allow users to setup according to other theories of proliferation/non-proliferation, such as domestic politics or national identity. This future model will have setup buttons that activate certain parts of the code but not others.

## NETLOGO FEATURES

## RELATED MODELS

Some of the coding in this model comes from Wilensky's "Virus on a Network" model, which is what gave me the idea to come up with this model.

## CREDITS AND REFERENCES

Ryan Nixon, Old Dominion University, PhD Candidate in International Studies (2017).

Ryan can be contacted at rnixo005@odu.edu for questions, suggestions, or comments.

Waltz, Kenneth Neal. The Spread of Nuclear Weapons More May Be Better. Adelphi Papers ; No. 171. London: International Institute for Strategic Studies, 1981.