Definition
The Earned Income Tax Credit (EITC) is the largest U.S. cash transfer program for low-income working families, delivered as a refundable federal income tax credit. It is structured as a nonlinear function of earned income with three regions: a phase-in range (where credit rises with earnings at 34–40%), a plateau (maximum credit sustained over a middle-income range), and a phase-out range (where credit falls at 16–21% as income rises above the plateau). In 2007, the maximum credit was $2,853 for families with one child and $4,716 for families with two or more children. Eligibility requires earned income; the credit phases to zero for higher earners. Approximately 22 million families receive the EITC annually.
Key Ideas
- Phase-in / plateau / phase-out structure: The EITC creates two major "kink points" in the budget constraint — one where the phase-in ends (first kink, optimal earnings range for maximizing credit) and one where the phase-out ends. Because the schedule is nonlinear, the effect on labor supply depends heavily on which region a worker is in.
- Extensive vs. intensive margin effects: The EITC is well-documented to increase labor force participation (extensive margin) substantially, especially among single mothers. Its effect on hours worked conditional on employment (intensive margin) is near zero or slightly negative — consistent with the phase-out creating an implicit marginal tax on workers already in the labor force.
- Information frictions: Less than 5% of EITC recipients know the nonlinear shape of the EITC schedule (Chetty and Saez 2009). Recipients know their current refund amount but not how marginal changes in earnings would affect their credit — a form of tax salience failure that partially explains why intensive-margin responses are muted.
- Tax professional mediation: The primary point of contact for EITC recipients with the tax system is their tax preparer. Tax professionals can translate the complex nonlinear schedule into actionable guidance — but only if they do so (Chetty and Saez 2009 find strong heterogeneity in whether professionals "comply" with an information intervention).
- Salience and optimization: Standard labor supply models predict bunching at the first kink (phase-in/plateau boundary) where the marginal subsidy drops to zero. Observed bunching is lower than predicted, consistent with incomplete information about the schedule shape. See Tax Salience.
How It Works
Budget Constraint Effect
The EITC adds a nonlinear income transfer on top of earnings. For a worker on the phase-in portion, each additional dollar earned returns 34–40 cents in credit — a substantial earnings subsidy. For a worker on the plateau, the marginal EITC return is zero. For a worker in the phase-out, each additional dollar reduces the credit by 16–21 cents, creating an implicit marginal tax rate above the statutory rate.
Labor Supply Incentives by Region
- Phase-in workers face an effective marginal subsidy and a positive income effect; both the substitution and income effect push toward more work.
- Plateau workers face no marginal change in credit; EITC operates as a pure income effect (ambiguous sign on hours).
- Phase-out workers face an implicit marginal tax; substitution effect pushes toward less work; income effect is positive but may be dominated.
Information Provision and Response
Chetty and Saez (2009) show that providing EITC schedule information through tax professionals shifts earnings toward the first-kink optimal range — but only when professionals actively transmit the information. The information treatment is equivalent in magnitude to a 33% expansion of the EITC or a 5.4 percentage-point reduction in the marginal tax rate (at intensive-margin elasticity =0.25).
Why It Matters
- Largest U.S. transfer program: The EITC transfers more to low-income working families than any other federal program; its design has direct implications for poverty, inequality, and the marginal cost of redistribution.
- Work incentive instrument: The EITC is the primary federal tool for incentivizing labor force participation among low-income parents; the large extensive-margin effect is among the most robust findings in labor economics.
- Intensive-margin puzzle: The near-zero intensive-margin response raises the question of whether the EITC's kink structure is irrelevant for hours optimization or whether information frictions, optimization costs, or institutional constraints suppress what would otherwise be a detectable response.
- Policy design implications: If information frictions are the binding constraint, the optimal policy response is to improve information delivery (e.g., through tax preparers, automatic notification) rather than to change the credit schedule. Chetty and Saez (2009) suggest that tax professional training could be a cost-effective supplement to EITC policy.
- Behavioral tax policy: The EITC is a central case study in the behavioral public finance literature on how complexity, salience, and intermediaries affect program take-up and incentive effectiveness. See Tax Salience and Optimal Social Insurance.
Open Questions
- What share of the zero intensive-margin response is information frictions vs. structural barriers (rigid hours, multiple jobs, childcare constraints)?
- Can tax professional training or automated EITC calculators replicate the complier effect at scale?
- Do self-employed filers respond differently to EITC information than wage workers? (Self-employment income is more flexible but also harder to verify.)
- Does the intensive-margin information effect persist beyond one year, or do recipients return to prior earnings patterns?
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