# Open-Source Data Models?

What could help people share the models they use for generating data so that others can investigate alternative scenarios or presentations of the model (and not just the resulting data)?

For example, in the The Economics of Structured Finance [pdf], Joshua D. Coval, Jakub Jurek, and Erik Stafford discuss the impact on the value of collateralized debt obligations (CDOs) and CDOs-squared of changes in the default correlation and probability of their underlying assets. They present one graph showing the change in value versus the change in default correlation, and another showing the change in value versus the change in default probability. But they don't show the change in value versus combinations of changes in default correlation and default probability. An open-source model would allow someone to calculate these hybrid scenarios, or even to create a visualization allowing others to explore the model in other ways.

To be relevant, of course, such an open-source model would need to be in a format accessible to those interested in using it. What tools do these models tend to be created in? If these are proprietary and expensive, an open-source model may be useful to other researchers and professionals, but not the broader public. Is it possible to make it easier to create or modify these models in free (e.g. most programming languages) or common (e.g. Microsoft Excel) tools?

Alternatively, it is enough to encourage the distribution of data resulting from such models, in the expectation that a comprehensive data set would enable most or all of the uses of an open-source model?

**Update:** This week's Planet Money discusses another possible audience for open-source (or, at least, shared) data models: rating agencies and investors. That is, rating agencies could publish the models and calculations they use to determine their ratings - giving investors an opportunity to evaluate their assumptions as well as their final judgements.