About the project
OpenFisca is a versatile microsimulation software.
It is a free software published under the GNU Affero General Public Licence version 3 or later.
What's the purpose?
OpenFisca allows users to calculate many variables of the tax and benefit legislation of a country (social benefits and taxes paid by households) given input variables. The impact of reform projects can also be simulated.
When plugged on a survey, OpenFisca can also calculate the budgetary consequences of a reform and its distributional impact.
Its engine is independent of the country, it is therefore possible to simulate any country. For now the main supported country is France.
OpenFisca is distributed with distinct packages:
- OpenFisca-Core allows to calculate variables in Python
- OpenFisca-France contains a representation of the French legislation
- OpenFisca-Web-API allows to calculate variables using an web API
OpenFisca is more a platform than an application: its first target is not the end user but economists, software developers, researchers, teachers, administrations, interested citizens, etc.
Final products can be built on the top of OpenFisca. They trigger tax and benefit variables computations via the web API. For example: Mes aides.
Then, the web API of OpenFisca is used by the team itself to develop tools like the legislation explorer.
These tools are designed to help developers understand the legislation when they write it down into source code, and allow citizens to browse the tax and benefit legislation.
The current version implements a large set of taxes, social benefits and housing provision for France for the last 10 years. But this is only due to a shortage in manpower to enter and update the Tunisian legislation.
The project is 100% free software, it is published on GitHub. It uses the GitHub infrastructure (issues, pull requests, etc.) to communicate internally or with external participants. The team discusses publically on those issues and pull requests and tries to be as transparent as possible.
The project is multi-actors: many people and organizations are involved in the project, reading the legislation and transforming it into source code, developing the Core or web tools, developing external products, etc.
OpenFisca provides a basic infrastructure, in particular a public instance of its web API, hosted on cheap servers. As it is free software, anyone can reproduce the OpenFisca infrastructure on its server.
What is microsimulation?
OpenFisca is written in the Python programming language.
OpenFisca can calculate tax and benefit variables on test cases (a person or a household) or population data (real data or survey data). To achieve both, computations are vectorial. For performance reasons the NumPy package is used. It is coded in the C language under the hood, more performant than Python.
The source code has been released under a free software license in November 2011.
OpenFisca was originally developed as a desktop application using the Qt library with a Python API.
In the early 2014, when Etalab started being implicated in the development of OpenFisca, it was decided to:
- separate the computing engine from its desktop user interface
- offer a web API in addition to the Python API
- demonstrate the value of the web API by developing sample applications including a web interface to simulate personal cases
- propose a public access to this web API open to all: administrations, researchers, citizens, etc.
Since then, the software is being developed extensively by Etalab. Meanwhile the economic model is being improved and the tax and benefit legislation updated by the CGSP with the help of the the IDEP and the IPP.
As of now (March 2014), the Qt version is no longer maintained and only the Python and the web APIs are being developed.