Candice Horbacz
Not all tax hikes bring in more revenue, a fundamental economic principle that underscores the intricate relationship between tax rates, taxpayer behavior, and the ultimate collection of government funds. Setting a tax rate too high might not yield as much revenue as a strategically lower rate, primarily because tax policies directly influence how much individuals work, save, and invest, and how businesses operate and grow—all activities that significantly affect the income tax base. This dynamic interplay compels economists and policymakers to meticulously search for the "Goldilocks rate," a tax level that is "just right" for maximizing public coffers without stifling economic activity. A new research paper by Rachel Moore, Brandon Pecoraro, and David Splinter delves into this critical question, offering fresh insights that suggest the income tax rate maximizing revenue may actually be lower than prior influential estimates indicated.
The Enduring Relevance of the Laffer Curve in Tax Policy Debates
At the heart of this discussion is the Laffer Curve, a theoretical representation developed by economist Arthur Laffer in the 1970s. The curve posits that as tax rates increase from zero, tax revenue initially rises, reaches a maximum point, and then begins to fall as rates climb further, eventually reaching zero revenue at a 100 percent tax rate. The underlying premise is that excessively high tax rates disincentivize economic activity, leading individuals to work less, invest less, or engage in tax avoidance, thereby shrinking the tax base and ultimately reducing the total revenue collected. Conversely, extremely low rates might not collect enough revenue despite high economic activity. The challenge for policymakers lies in identifying the peak of this curve—the point at which the marginal tax rate extracts the maximum possible revenue.
Historically, the Laffer Curve has been a cornerstone of supply-side economics, influencing policy debates particularly during the Reagan administration in the United States. While its general shape is widely accepted in economic theory, the precise location of its peak—and thus the revenue-maximizing tax rate for a specific economy—remains a subject of intense empirical investigation and often contentious debate. Factors like the elasticity of the tax base (how responsive economic activity is to changes in tax rates), the breadth of the tax base, and the specific structure of a nation’s tax system all play crucial roles in determining this elusive optimal rate. Understanding these dynamics is vital for governments seeking to balance fiscal needs with economic growth objectives, especially when considering significant tax reforms or adjustments to top marginal rates.
A Decade of Shifting Perspectives: From Diamond and Saez to Current Research
The academic pursuit of the Laffer Curve’s peak gained significant momentum in the early 21st century, culminating in seminal work that has profoundly shaped contemporary discussions on optimal taxation. A particularly influential contribution came in 2011 from economists Peter Diamond and Emmanuel Saez, whose paper, "The Case for a Progressive Tax," published in the Journal of Economic Perspectives, aimed to empirically identify the peak of the Laffer Curve for the U.S. economy. Building on Saez’s earlier theoretical frameworks, their research estimated a top revenue-maximizing marginal tax rate of 73 percent. This figure quickly permeated policy discussions, becoming a frequently cited benchmark in debates about increasing taxes on high-income earners.
However, the findings of the Diamond and Saez paper were often subject to significant misinterpretation by policymakers and commentators alike. A common misunderstanding was the belief that the 73 percent figure represented the optimal top federal individual income tax rate that should be implemented. The reality, as clarified by the authors themselves and subsequent analyses, was far more nuanced. Firstly, the 73 percent estimate was an aggregate figure, encompassing all taxes levied at the federal, state, and local levels, including payroll taxes, sales taxes, and various income taxes. It did not suggest that simply raising the top federal income tax rate (which was around 35 percent at the time) to 73 percent would maximize revenue.
Secondly, and critically overlooked, the 73 percent estimate relied on the assumption of a significantly broader tax base than what existed in the U.S. at the time, or what exists today. This hypothetical broad base would have eliminated numerous deductions, credits, and preferential tax treatments that narrow the actual taxable income. When Diamond and Saez applied their model to the existing, narrower U.S. tax base, which includes various exclusions and special provisions, their estimate for the top revenue-maximizing rate dropped to 54 percent. Furthermore, if only the top federal income tax rate was considered within the existing narrow base, the estimated peak fell to 48 percent. For context, this 48 percent figure was not drastically higher than the combined federal and state income tax rates already faced by high-income taxpayers in states like New York and California, illustrating the importance of considering the full tax burden across jurisdictions.
Unpacking Behavioral Responses: The Flatter Laffer Curve Hypothesis
Despite the influence of Diamond and Saez’s work, the academic discourse on optimal tax rates continued to evolve. Numerous papers published in the years following 2011 explored different methodologies and assumptions, yielding a wide range of estimates for total government revenue-maximizing tax rates from all sources, typically falling between 46 percent and 73 percent. This variability underscored the complexity of the issue and the sensitivity of the results to specific modeling choices.
In this context, the new paper by economists Rachel Moore, Brandon Pecoraro, and David Splinter offers a significant refinement. Their research, building upon previous studies, critiques prior approaches for often using tax bases that were either too broad or too narrow, crucially failing to fully capture important behavioral adjustments by taxpayers. The central argument of their work is that, given the current intricacies of the U.S. tax system, the Laffer curves are actually flatter than estimated by Saez and other authors. A flatter curve implies that the revenue gains from increasing top tax rates are considerably smaller than what previous, more optimistic estimates might suggest.
The core of Moore, Pecoraro, and Splinter’s improved methodology lies in their meticulous construction of different tax bases and their use of detailed administrative data covering high-income taxpayers. This granular approach allows them to estimate a more comprehensive array of behavioral responses to changes in tax rates. One key insight is that policymakers are often focused on changes to the top ordinary income tax rate, yet a substantial portion of income at the top of the distribution falls outside this specific tax base. For instance, while the ordinary income tax base includes certain types of capital income, such as short-term capital gains and profits from pass-through businesses (like S corporations or partnerships), other significant forms of capital income, such as long-term capital gains and qualified dividends, are taxed at preferential, lower rates. Furthermore, the ordinary income tax base is perpetually reduced by various deductions and credits designed to encourage specific types of investment or activities.
Illustrating Margins of Adjustment: How Taxpayers Respond
The authors’ model is designed to capture these diverse "margins of adjustment" that taxpayers utilize in response to changes in tax rates. These behavioral responses are not merely theoretical constructs but observable actions taken by individuals and businesses to optimize their after-tax income. For example, corporations might strategically switch their organizational forms to non-corporate structures, such as pass-through entities, if tax rates on pass-through business income become more favorable relative to corporate rates. This reclassification allows income to be taxed at individual rates, potentially circumventing higher corporate levies. Similarly, individual income taxpayers, especially those in higher brackets, tend to increase their engagement in tax-deductible activities—such as charitable giving, contributions to retirement accounts, or investment in specific tax-advantaged vehicles—when their marginal tax rates rise. These actions, while potentially beneficial in other contexts, effectively reduce their taxable income and, consequently, the revenue collected by the government.
By accounting for these and other additional margins, the new research finds that the revenue losses stemming from federal rate increases are roughly double compared to previous estimates that relied on a single, less nuanced tax base. This doubling of estimated revenue loss highlights the sensitivity of the tax base to behavioral changes and the limitations of models that do not fully incorporate these responses. The implication is profound: policymakers who assume a relatively inelastic (unresponsive) tax base when raising rates might significantly overestimate potential revenue gains.
New Quantitative Findings and Policy Implications
Moore, Pecoraro, and Splinter’s paper provides specific quantitative estimates that challenge existing assumptions. When using a single, broad tax base—similar to some previous models—their analysis yields a revenue-maximizing federal income tax rate of 55 percent. However, when they transition to using multiple tax bases and fully account for all possible behavioral responses (what they term the "true" base), the estimated revenue-maximizing federal income tax rate falls significantly to 48 percent. At this 48 percent rate, their model projects an additional $43 billion in revenue, which represents approximately 0.2 percent of the nation’s Gross Domestic Product (GDP). This figure, while substantial, is lower than what a 55 percent rate might suggest without considering the broader behavioral shifts.
The findings become even more striking when considering the entire tax ecosystem, encompassing all taxes at the federal, state, and local levels. The top federal individual income tax rate that would maximize total government revenue from all sources is estimated to be even lower, at 39 percent. A move to this 39 percent rate from the current level would yield only about $1 billion in additional total tax revenue. This marginal gain is largely due to a critical offsetting effect: the losses incurred by state and local revenue streams almost fully negate the gains observed at the federal level. This delicate balance underscores the interconnectedness of different tax jurisdictions and the potential for federal policy changes to have unintended consequences on sub-national governments. For context, the current top federal individual income tax rate is 37 percent, meaning that a move to the theoretically revenue-maximizing rate of 39 percent offers minimal additional revenue when considering the broader fiscal landscape.
The overarching conclusion of this new research is clear: raising top income tax rates on the current, complex tax base may not yield as much revenue as previous estimates suggested. This discrepancy is largely attributable to the ample opportunities for high-income taxpayers to strategically shift income to different tax bases or utilize various deductions and credits within the existing tax code. For policymakers contemplating increases in tax rates on high-income individuals, the paper serves as a crucial reminder that such changes, if not accompanied by comprehensive reforms to the underlying tax code (such as broadening the tax base or harmonizing rates across different income types), are likely to generate diminishing returns.
Broader Implications for Tax Reform and Economic Strategy
The findings of Moore, Pecoraro, and Splinter have significant implications for ongoing discussions about tax reform and national fiscal strategy. They reinforce the notion that tax policy is not merely about adjusting rates but about understanding the dynamic responses of economic actors.
Firstly, the research underscores the challenges of revenue estimation. Government budget projections often rely on static scoring, which assumes taxpayer behavior remains constant despite tax changes, or dynamic scoring that may not fully capture all behavioral adjustments. The new paper highlights the need for sophisticated dynamic models that account for a wide array of income shifting and deduction responses, ensuring more accurate revenue forecasts.
Secondly, it reignites the debate on tax base broadening. If the "flatter" Laffer curves are indeed accurate, then efforts to increase revenue might be more effectively directed at closing loopholes, eliminating preferential treatments for certain types of income (like capital gains), and simplifying the tax code to reduce opportunities for income shifting. A broader, more uniform tax base, even at lower rates, could potentially yield more stable and predictable revenue streams. This aligns with the original nuance in Diamond and Saez’s work, which also identified higher revenue-maximizing rates under a broader, hypothetical tax base.
Thirdly, the paper implicitly highlights the trade-offs inherent in tax policy. While maximizing revenue is a critical objective for funding public services and reducing deficits, it is not the only goal. Policymakers must also consider the impact of tax rates on economic growth, investment incentives, income inequality, and administrative complexity. A tax rate that maximizes revenue might not necessarily be the rate that optimizes overall economic welfare or achieves desired social objectives. For instance, extremely high rates, even if theoretically revenue-maximizing in a narrow context, could deter entrepreneurship and capital formation in the long run.
Finally, the proximity of the current top federal income tax rate (37 percent) to the newly estimated total government revenue-maximizing rate (39 percent) suggests that there may be limited additional revenue to be gained by simply pushing the top federal rate marginally higher without addressing the broader structural issues of the tax code. Any significant increase beyond this point risks moving further down the "wrong side" of the Laffer Curve, leading to actual revenue losses, particularly when considering the cascading effects on state and local revenues.
In conclusion, the new research by Moore, Pecoraro, and Splinter provides a vital update to the understanding of optimal tax rates in the United States. By rigorously accounting for the diverse behavioral responses of high-income taxpayers within the existing, complex tax code, they demonstrate that the revenue-maximizing rates may be lower than previously believed, and the gains from increasing top rates potentially more modest. This sophisticated analysis serves as a critical guide for policymakers, emphasizing that genuine and sustainable revenue generation often requires comprehensive tax reform that addresses the intricacies of the tax base and taxpayer behavior, rather than simply adjusting headline rates in isolation.
