Tax Model Frequently Asked Questions (FAQ) and Other Resources
These documents provide a description of the Tax Policy Center's microsimulation model of the federal tax system and materials to help understand and interpret our estimates.
Answers to common questions about TPC's tax simulation model, the estimates it generates, and the organization of tables in our database.
- Brief Description of the Tax Model
An abbreviated explanation of the current version of TPC's tax simulation model.
- Methodology for "Off-Model" Revenue Estimates
An in-depth description of how TPC estimates off-model revenue estimates, except for broad-based consumption taxes.
- Tax Model Documentation
A detailed description of an earlier version of TPC's tax model. This document describes the methodology we use to create the model's database and explains the capabilities of the model's tax calculator.
- How to Interpret Distribution Tables
Definitions of the various measures of the distributional impacts of a tax change that TPC displays in our standard tables.
- Explanation of Income Measures
A detailed definition of Expanded Cash Income (ECI), the income measure TPC currently uses in our distribution tables, and a description of other income measures we have used in the past.
- Explanation of Baselines
A detailed definition of TPC's current law baseline and a description of other baselines, such as "current policy", that we have used in the past.
- Income Breaks for Distribution Tables
A table that shows the income levels that define the percentile ranges in our distribution tables for all years from 2004-2024. We provide ranges for three income measures: Adjusted Gross Income (AGI); Expanded Cash Income (ECI); and ECI adjusted for family size.