REVIEW 3 major objections 3 minor 1 cited by
Why Ethereum Needs Fairness Mechanisms that Do Not Depend on Participants' Altruism
T0 review · 3 major / 3 minor · reviewed 2026-08-02 · deepseek-v4-flash
Pith's one-line read An empirical study of 600,115 Ethereum block proposers concludes that at most 1.36 percent are plausibly altruistic, not the commonly read 9 percent; committee-based fairness mechanisms would need at least 128 members.
desk verdict Solid empirical upper bound on altruistic proposers, but the abstract oversells and the committee-size math outruns the measurements. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing instrument is a six-stage exclusion pipeline that turns the unobservable moral trait 'altruism' into an observable negative: a proposer is (potentially) altruistic only if none of the six classifiers flag it. The classifiers remove, in order, proposers whose blocks were mediated by relay-based block construction services; proposers sharing a common reward-recipient (governance) cluster with a relay user or with a contract-account or builder-payment address; proposers including non-public (exclusive-order-flow) transactions; and proposers whose blocks are not strictly ordered by descending priority fees. The final condition is the subtle one: strict fee ordering is the defaul
What would settle it
Offer a permissionless bribe contract on a testnet fork of Ethereum that pays any proposer a premium for excluding a designated transaction from an inclusion-list challenge, then record how many of the 3,814 proposers classified as altruistic accept it. If a significant share accepts, or if those proposers later start using relay-mediated block construction once local construction becomes less profitable, the 1.36% upper bound is not a bound on bribe-resistant altruism.
Extended reading notes
Core claim
On the authors' own terms, the discovery is that altruistic proposers exist but are rare: 0.71% of observed proposers show no indication of any non-altruistic behavior, and even the most generous reading, the set of 'potentially altruistic' proposers, is 1.36% (the abstract rounds to 1.55%). After classifying all 859,313 blocks in the January–April 2025 window, the paper finds that 98.64% of proposers exhibit observable non-altruistic behavior of one of six kinds. It interprets the residual as an upper bound, not a point estimate, because borderline cases are classified conservatively. The paper's central consequence is that the commonly used 9% altruism estimate is almost an order of magnit
Load-bearing premise
The load-bearing premise is that absence of observable profit-seeking behavior equals willingness to forgo revenue and comply with a fairness mechanism; in particular, the paper counts strict descending priority-fee ordering — itself a profit-maximizing default heuristic of most clients — as the altruistic signal, so the 1.36% figure is an upper bound on detectable non-altruism, not a measure of bribe-resistant altruism.
Editorial extensions
If this is right
- A 16-member inclusion-list or concurrent-proposer committee would contain at least one altruist with probability about 20.7%, not the 77.9% implied by the 9% reading; mechanisms proposed at that size are unlikely to deliver the promised censorship resistance.
- Reaching an 83.5% probability of an altruistic member requires committees of at least 128, a size that dilutes individual influence and makes the mechanism harder to coordinate and reason about.
- Because 98.64% of proposers show observable profit-seeking behavior, any mechanism that makes compliance costly will face near-universal defection unless fairness is made the financially rational strategy via rewards, penalties, or accountability.
- Under enshrined proposer-builder separation, the rationality properties of proposers do not change: proposers who already chose rational delegation will not suddenly intervene, so the altruism bottleneck persists.
- The altruistic pool skews toward validators registered before the proof-of-stake transition; as that cohort shrinks, the effective altruism share is likely to fall, so committee sizes may need to grow over time.
Reading between the lines
- My reading: the paper's own Method VI weakens the estimate it claims. Strict descending priority-fee ordering is a profit-maximizing default heuristic of most consensus clients, so a rational proposer running default settings produces exactly the 'altruistic' signature. The 1.36% figure is therefore an upper bound on 'no observed non-altruism,' not on bribe-resistant altruism.
- If the altruism signal is partly a default-configuration artifact, the true bribe-resistant share could be below 0.71%, and the committee-size calculation would be even more pessimistic.
- A natural extension the authors leave implicit: use their classifier on a testnet with a live bribe challenge (a transaction that pays out if a certain address is excluded) to measure actual compliance among the 3,814 'altruistic' proposers.
- Another extension: resample the same six classifiers at future dates; if the altruist share declines with validator turnover, mechanism designers should not treat 1.36% as a stable floor.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper estimates the prevalence of 'altruistic' Ethereum block proposers — proposers who, in the authors' definition, follow the protocol without deviation and could plausibly support committee-based fairness mechanisms such as Inclusion Lists and Multiple Concurrent Proposers. Using four months of Ethereum data (859,313 blocks, 600,115 proposers), the authors apply a cascade of classifiers to exclude proposers who use MEV-Boost relays, share governance with relaying proposers, are contract accounts, receive builder payments, include exclusive order flow, or do not order transactions by descending priority fees. They report that at most 1.36% of proposers (abstract: 1.55%) provide no clear evidence of non-altruistic behavior, and use this rate to argue that a 128-member committee would give only about an 83.5% probability of containing at least one altruistic member. The paper concludes that committee-based fairness mechanisms relying on altruism require substantially larger committees than currently proposed and that incentive- or penalty-based mechanisms are needed.
Significance. If the measurement is valid, the paper makes an important empirical contribution to Ethereum mechanism design: it challenges the commonly cited ~9% altruistic-proposer figure and provides a concrete, reproducible exclusion pipeline. The authors are appropriately careful in several places — they repeatedly frame 1.36% as an upper bound, acknowledge that de-anonymization could reveal cluster overlap, and make analysis scripts publicly available. The study is directly relevant to ongoing IL/MCP committee-size proposals. However, the central quantity the paper needs — the share of proposers who would comply with a fairness mechanism even at personal financial cost — is not directly measured, and one of the positive classifiers (strict priority-fee ordering) is, by the paper's own admission, the profit-maximizing default of most consensus clients. This weakens the quantitative committee-size claim, even though the qualitative conclusion that reliance on altruism is fragile appears robust.
major comments (3)
- [§3.3 (Method VI) and §5] Method VI labels strict descending priority-fee ordering as a positive signal of altruism, despite the paper's own statement that this ordering 'aims to maximize proposer profits' and is the default heuristic of most consensus clients. A rational proposer running an unmodified client produces exactly the 0.65% signature counted as altruistic. The 0.71% with non-strict but strongly correlated ordering are 'not clearly altruistic' in Figure 2, yet are included in the 1.36% used in Section 5 to compute 1−0.986^128 ≈ 83.5%. The 128-member figure is therefore an upper-bound probability under a generous definition, not a reliability guarantee; if the true bribe-resistant rate is lower, a 128-member committee may fall well below 83.5%. The qualitative 'larger committees are needed' conclusion survives, but the concrete 128/83.5% claim must be re-derived with a defensible parameter and clearly f
- [Abstract vs. body (§3, §4)] The abstract states 'full year 2025' and 'at most 1.55 percent of proposers', while the introduction and results consistently describe a four-month window (January–April 2025) and report 1.36% (0.65% strict altruistic and 0.71% potentially altruistic). These are materially different claims. The paper needs to reconcile the observation period and explain why the abstract's headline number differs from the body's 1.36%. This is not merely a typo, because the committee-size calculation in the abstract and Section 5 depends on the exact rate.
- [§4.1–§4.3] Many classifications rest on extremely thin individual evidence: the 47,216 non-relaying proposers have a median of exactly one proposed block, and the 3,814 'altruistic' proposers are classified from strict ordering in 'all proposed blocks' — which for a one-block proposer is a single observation. No sensitivity analysis is provided for the Spearman threshold (σ_rs > 0.7), the tie-handling epsilon, or the decision to exclude only proposers rather than clusters for classifiers V and VI. Since one default-configured block passes the strict-order test, the paper should report the block-count distribution for the 3,814 altruistic proposers and show how the 1.36% rate changes under reasonable threshold variations.
minor comments (3)
- [Figure 2] The figure labels the 0.71% share as 'not clearly altruistic' while the text in §4.3 says these proposers are 'also likely altruistic'. The terminology ('altruistic', 'potentially altruistic', 'not clearly altruistic') should be harmonized.
- [§4.3] The sentence 'Excluding all clusters containing at least one proposer with detected XOF activity would yield a value of 0.57 %' is presented without derivation; please define the baseline and clarify whether this is a cluster-level or proposer-level number.
- [§5, Validity under ePBS] The claim that proposers who previously outsourced block production 'would adopt this deviation' in the future is a behavioral inference, not a measurement. The paper should distinguish more sharply between observed past behavior and predicted future compliance with an incentive-compatible fairness mechanism.
Circularity Check
Headline altruism share is defined as the residual of the exclusion pipeline; Method VI further counts profit-maximizing default ordering as altruism, so the 83.5% committee reliability figure is partly an artifact of the classifier definition.
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self definitional
[Section 3 Methodology / Section 6 Conclusion]
"Proposers are classified as altruistic if they neither use MEV-Boost relays nor participate in shared governance with already excluded proposers, and if their blocks yield only protocol-intended rewards, i.e., block rewards and priority fees. ... We find that roughly 98.64 % of proposers behave non-altruistically, while only 1.36 % provide no clear evidence of such behavior."
The classification defines 'altruistic' as the complement of a set of exclusion criteria, so the reported 1.36% is the residual of the pipeline by construction. The conclusion that '98.64% behave non-altruistically' is then just the complement of the not-excluded set, even though the paper's own Classifier VI explicitly 'does not imply non-altruism.' Thus the headline share is equivalent to the chosen operationalization rather than an independent measure of altruism.
-
self definitional
[Section 3.3, Method VI]
"Such an ordering aims to maximize proposer profits and reflects a simple heuristic implemented by most consensus clients. Although this ordering is profit-maximizing, we classify the corresponding proposer as altruistic, since the heuristic depends solely on protocol-defined attributes."
The positive signal for 'altruistic' is defined as the standard profit-maximizing client default (descending priority-fee ordering). A rational proposer using default client settings therefore automatically satisfies the altruism criterion, so the measured 'altruistic' set is populated by construction with profit-maximizing behavior. The later committee-size calculation (1 − 0.986^128 ≈ 83.5%) inherits this definitional inflation, making the reliability estimate an artifact of the classifier rather than an independent measure of bribe resistance.
full rationale
The paper is transparent about its methods and explicitly labels 1.36% as an upper bound, and the self-citations are not load-bearing. However, the central quantity is definitionally constructed: 'altruistic' is operationalized as 'not excluded by the pipeline,' and Method VI specifically counts the profit-maximizing default ordering as altruistic. Consequently, the headline '98.64% behave non-altruistically' and the '128 members / 83.5%' committee probability are restatements of the classifier assumptions rather than independent empirical findings. The paper's own caveats—Classifier VI does not imply non-altruism, and the method may overestimate altruism—confirm that the strong conclusion goes beyond what the measurement can support. This is a partial circularity, not a citation-chain or uniqueness-theorem problem.
Assumptions & free parameters
free parameters (5)
- Altruism definition (behavioral proxy chain) =
no MEV-Boost use; no shared governance with relaying proposer; EOA-only cluster; no builder payments; no XOF; strict fee
- Spearman threshold (classifier VI) =
0.7
- Monitored relay set =
6 relays (Aestus, Agnostic, bloXroute ×2, Flashbots, Ultrasound, Titan)
- Tie-handling epsilon in σ_rs =
unspecified 'ε > 0 accounting for ties'
- Altruism rate used in committee sizing =
1.4% (the potentially-altruistic share)
assumptions (7)
- domain assumption Any use of MEV-Boost relay mediation is non-altruistic behavior (delegation of block contents to a profit-maximizing builder).
- domain assumption A proposer sharing a coinbase cluster with a relaying proposer is non-altruistic (guilt by governance association).
- domain assumption All contract-account coinbase clusters are STaaS setups with non-altruistic managing parties.
- domain assumption Strict descending maxPriorityFeePerGas ordering evidences altruism.
- domain assumption Transactions absent from the Mempool Guru dataset are exclusive order flow (XOF) included for profit.
- standard math Committee membership is effectively independent/random for the binomial probability 1 − p^n.
- standard math Spearman rank correlation is an appropriate content-independence / altruism metric.
Cite this review
Pith. "Pith review of Why Ethereum Needs Fairness Mechanisms that Do Not Depend on Participants' Altruism." pith.science (2026). https://pith.science/paper/ZK4UZ7AV
@misc{pith2026260305666,
author = {Pith},
title = {Pith review of: Why Ethereum Needs Fairness Mechanisms that Do Not Depend on Participants' Altruism},
year = {2026},
howpublished = {\url{https://pith.science/paper/ZK4UZ7AV}},
note = {Machine review of arXiv:2603.05666}
}
read the original abstract
Ethereum's ideal of censorship resistance, together with related fairness properties, is undermined in practice, motivating fairness mechanisms that aim to restore these properties. Several of these mechanisms hand control over block contents to a committee of proposers under a 1-of-n honest assumption: at least one committee member complies with the mechanism even when deviating would increase personal revenue. We refer to such proposers as altruistic. Yet prior work shows that roughly 91 percent of blocks are constructed by centralized block-building services that demonstrably take user-adverse actions for financial gain; the responsible proposers sign these blocks blindly, without any means of intervention. A common reading of this figure is that 9 percent of proposers forgo these gains and act altruistically. Our empirical analysis of the full year 2025 shows that this share is far smaller: at most 1.55 percent of proposers can plausibly be regarded as altruistic, whereas the remaining 98.45 percent of proposers exhibit observable non-altruistic behavior. We interpret 1.55 percent as an upper bound on the prevalence of altruistic proposers. These results imply that committee-based fairness mechanisms that rely on altruistic members would require substantially larger committees than currently proposed. This raises concerns about their practical viability and motivates mechanisms in which fair behavior is the rational choice.
Figures
Forward citations
Cited by 1 Pith paper
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Accountable Transaction Inclusion Lists: Enhancing Ethereum's Censorship Resistance
FairFIL makes multi-block censorship costly by requiring builders to disclose excluded transactions and forcing the next block to include them, with loss of the whole block reward for omissions.
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Reviewed August 2, 2026 · model on record in the stance chip above.
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