Introduction

This is the documentation for PolicyEngine Core, the open-source Python package powering PolicyEngine’s tax-benefit microsimulation models. It is a fork of OpenFisca-Core, developed and maintained by OpenFisca.

PolicyEngine Core does not simulate any specific tax-benefit policy: instead, it is a general framework for building tax-benefit microsimulation models. It is currently used by PolicyEngine UK and PolicyEngine US, which each define the custom logic, parameters and data required to simulate the tax-benefit systems of the UK and the US respectively.

The country models each provide:

• A set of entity types (e.g. Person).

• A set of parameters (e.g. parameters.tax.flat_tax.rate). Parameters are global data points that have different values for different time periods.

• A set of variables (e.g. income_tax). Variables are properties of entities that can be dependent on entities (including other variable values), parameters and the time period.

PolicyEngine Core then enables users to:

• Calculate the value of a variable in a specific time period.

• Trace the computation tree of a calculation.

PolicyEngine Core also includes many helper functions designed to simplify the process of modelling a country’s policy.