# System Dynamics

Insight Maker supports System Dynamics modeling: a powerful method for exploring systems on an aggregate level. By "aggregate", it is meant that System Dynamics models look at collections of objects, not the objects themselves. For instance, if you created a model of a water leakage from a bucket, a System Dynamics model would concern itself with the quantity of water as a whole, not with individual droplets or even molecules. Similarly, if you were modeling a population of rabbits, the System Dynamics model would look at the population as a whole, not at the individual rabbits.

System Dynamics models are constructed from a set basic building blocks also known as "primitives". The key primitives are Stocks, Flows, Variables and Links.

Stock | Stocks store a material. For instance a bank account is a Stock that stores money. A bucket is a Stock that stores water. A population is a Stock that stores people. |
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Flow | A Flow moves material between stocks. For instance, in the case of a bank account you could have an inflow of deposits and an outflow of withdrawals. |

Variables | Variables are dynamically calculated values or constants. In the bank account model you could have a Variable representing the interest rate. It could be a fixed value or be governed by an equation that changed over time. |

Links | Links show the transfer of information between the different primitives in the model. If two primitives are linked, they are related in some way. |

From these basic primitives, and the others supported by Insight Maker, you can build both simple and complex models in a straightforward manner. Models related to ecology, policy, business, or many other fields are all possible. As an example of a simple model built using the System Dynamics features of Insight Maker, below is an embedded model showing the interactions between wolves and the moose they prey on at the Isle Royale in the Great Lakes. This model shows very interesting oscillatory behavior as the two species interact over time.

System Dynamics modeling is sometimes referred to as dynamical systems modeling or, simply, differential equation modeling as differential equations are at the heart of the technique.