For microsimulation, use policyengine.py. Society-wide microsimulation — population aggregates and distributional or budgetary impacts — is moving to the managed policyengine.py bundle, which pins certified, calibration-gated datasets. Direct microsimulation via policyengine-us (Microsimulation()) is deprecated and being migrated to policyengine.py. This package remains the home of the US tax-benefit rules and household-level calculations. Microsimulation results are estimates — inspect dataset calibration at https://calibration-diagnostics.vercel.app/populace.

PolicyEngine US is a microsimulation model of the US state and federal tax and benefit system.

PolicyEngine US supports Python 3.11 through 3.14 and requires pandas 3 or later. To install, run pip install policyengine-us.

To install PolicyEngine US as part of a certified PolicyEngine bundle, use the bundle installer published by policyengine, for example:

uvx --from policyengine policyengine bundle install --country us --venv .venv