REVIEW 3 major objections 5 minor 22 references
How the interplay between power concentration, competition, and propagation affects the resource efficiency of distributed ledgers
T0 review · 3 major / 5 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read Bitcoin's natural fork rate reduces, to first order, to one formula in propagation time, total hash power, and mining concentration.
desk verdict A clean analytical fork-rate formula with a genuinely new HHI factorization, softened by an acknowledged synchronized-start assumption and a somewhat post-hoc empirical validation. 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 object is the joint distribution of the first two order statistics of $N$ independent exponential mining clocks. The paper computes the density of the gap $\Delta$ between the two fastest miners (Eq. 5); evaluating that density at $\Delta = 0$ gives $\Lambda(1-\mathrm{HHI})$, and the first-order Taylor expansion of the gap's cumulative distribution then yields $C(\Delta_0) \approx \Delta_0 \Lambda (1 - \mathrm{HHI})$ (Eq. 8). The Herfindahl-Hirschman index $\mathrm{HHI} = \sum_i (\lambda_i/\Lambda)^2$ is the single summary of hash-rate heterogeneity that enters the formula, and the empirical pipeline that feeds it — estimating $\lambda_i$ from mined-block counts, fitting exponential, log-normal, and truncated power-law null distributions by the method of moments, plus a semi-empirical Bayesian posterior for the hash rates — is what allows the comparison with observed fork rates.
What would settle it
Measure, over many blocks on the live network, the actual times at which each mining pool begins hashing the new tip (for example from stratum traffic or pool-published timestamps), and compare the empirical distribution of the gap between the two fastest solutions with the prediction of Eq. (5) built from the same $\{\lambda_i\}$; if the measured gap distribution is systematically wider when propagation is slow, the synchronized-start premise fails and the first-order fork formula with it. A cheaper, already available check: in periods where the paper's Fig. 6b yields negative implied HHI, the inversion of Eq. (8) is meaningless, and those episodes are the places a staggered-start correction would have to bite.
Extended reading notes
Core claim
The paper derives the probability that two miners solve a block within a propagation-time window. Writing each miner's mining time as an independent exponential clock with rate $\lambda_i$, the gap between the first two successful miners has a distribution whose density at zero equals $\Lambda(1-\mathrm{HHI})$, so for small propagation delays the fork rate is $C(\Delta_0) \approx \Delta_0 \Lambda (1 - \mathrm{HHI})$. The authors validate this against Bitcoin data from 2015 to 2024: with $\Delta_0$ taken as the time to reach 50% of the network, predicted fork rates are comparable with the measured stale-block rate. They further show that empirical hash rates over the decade follow a truncated power law, consistent with a rich-get-richer dynamic capped by total energy supply, that the number of active mining pools fell from about 100 to about 35 while concentration rose, and that these two trends partly offset each other, leaving falling propagation time as the dominant driver of the decline in fork rates. On the security side, the model's inversion — implied $\Delta_0$ and implied HHI — gives a diagnostic: periods where the implied values contradict the measured ones indicate miners with better-than-median connectivity, intra-pool coordination, or strategic behaviour such as selfish mining.
Load-bearing premise
The model hinges on every miner beginning to mine the next block at the same instant, so the first two solutions behave like the first two order statistics of independent exponential clocks; staggered starts in the real network would change the gap distribution and could break the clean $\Delta_0 \Lambda (1-\mathrm{HHI})$ dependence — an assumption the authors explicitly flag as 'relatively strong' in the Discussion.
Editorial extensions
If this is right
- Fork rates in any Proof-of-Work ledger can be estimated directly from three measurable quantities — propagation time, total hash rate, and the HHI of the mining distribution — without simulating the consensus protocol.
- The observed drop in Bitcoin's fork rate from roughly 1% in 2015 to about 0.1% today is attributable mainly to faster block propagation, because the opposing effects of fewer miners and greater concentration have largely cancelled out.
- Higher hash-rate concentration suppresses natural forks, so a ledger designer faces an explicit trade-off: accept more waste and orphaned blocks for a more decentralized mining population, or accept centralization risk for smoother consensus.
- Because the formula can be inverted, deviations between measured and implied fork rates become detection signals for non-competitive behaviour — selfish mining, block withholding, or a network core in which miners learn of blocks faster than the median node.
- For faster blockchains where the ratio of propagation time to expected mining time exceeds about 0.4, the linear approximation degrades and the full order-statistics expression — including the hash-rate distribution's shape — must be used.
Reading between the lines
- The identity $p(0) = \Lambda(1-\mathrm{HHI})$ is a statement about any race between exponential clocks, not only blockchains: wherever the gap between the first two finishers determines wasted work or a tie-break, such as sharded block production, DAG ordering, or replicated commit protocols, the same concentration discount should appear.
- Because Eq. (8) needs only the fork rate, $\Delta_0$, and $\Lambda$, it could serve as a passive monitor of effective mining concentration in ledgers that do not publish pool attribution — a use the paper gestures at but does not develop.
- A direct way to probe the model's limits is to relax the synchronized-start assumption in simulation by drawing each miner's start time from the observed propagation kernel; the deviation from $\Delta_0\Lambda(1-\mathrm{HHI})$ should grow with the spread of start times, and the episodes in the paper's Fig. 6b where implied HHI turns negative are a natural place to look for exactly that failure.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes an analytical model for the rate of soft forks in Proof-of-Work blockchains with heterogeneous miners. The central result is Eq. (8), C(Δ0) ≈ Δ0 Λ (1 − HHI), which expresses the fork probability as the product of the propagation-time threshold, the total hash rate, and a concentration term. The model is tested against Bitcoin data on mining-pool shares, block propagation times, and stale blocks, and is used to argue that both greater hash-rate concentration and lower propagation time reduce fork rates. The paper also fits exponential, log-normal, and truncated power-law distributions to empirical hash rates and uses the model to extrapolate fork rates under different miner counts and hash-rate dispersions.
Significance. The analytical result is clean and potentially useful: if valid, Eq. (8) gives a simple, falsifiable relationship between an observable fork rate and measurable aggregates (total hash rate, propagation time, and HHI). The derivation from exponential order statistics to Eqs. (6)–(8) is mathematically sound under the stated assumptions, and the simulations in Fig. 10 confirm the analytical formulas for several hash-rate distributions. The empirical contribution is more mixed: the hash-rate distribution analysis and the historical concentration trend are informative, but the central validation claim that model-estimated fork rates are 'comparable with the empirical stale blocks rate' is weakened by the rescaling of the fork-rate data and by the posterior choice of the 50% propagation-time percentile. The stress-test concern about synchronized miner starts lands: it identifies a potentially load-bearing assumption that is acknowledged but not quantified.
major comments (3)
- [§2, Eqs. (1)–(8); §3 Discussion] The central approximation C(Δ0) ≈ Δ0 Λ (1 − HHI) is derived from N exponential clocks that all start at t = 0. In a real network, miner i can begin working on a new block only after receiving it, so its completion time is better described as T_i = S_i + E_i, where S_i is the arrival time of the previous block at miner i and E_i ~ Exp(λ_i). Once the S_i are non-degenerate, the joint law of the two smallest T_i is not the common-start order-statistic law in Eqs. (1)–(6), and the HHI factorization in Eq. (7) relies on the memoryless property of synchronized exponentials. The paper acknowledges this in the Discussion ('the relatively strong assumption that miners start mining at the same time'), but it does not quantify the error. Please add a sensitivity analysis, for example simulating T_i = S_i + E_i with S_i drawn from an empirically plausible propagation-time distribution or a two-miner calculation with fixed start-time offsets, and report how C(Δ0) and its HHI dependence change. Without such a check, the claim that Eq. (8) is validated in the regime of interest is not established.
- [§4.1.2, Fig. 4] The empirical validation is not independent as presented. The fork-rate series is rescaled by a constant factor 1.476 so that its value in February 2016 matches the 0.41% value from Gervais et al. [18], and the comparison in Fig. 4b uses Δ0 = Δ0^(50), a choice made after inspecting the agreement with the model. Therefore the match in Fig. 4b is not a free prediction: one point is imposed by construction, and the time-series agreement is not out-of-sample. Please show the raw, unrescaled fork-rate series, and either preselect Δ0 on a training period and evaluate on the remainder or otherwise provide an out-of-sample test. The current Fig. 4b supports only the weaker statement that the model is compatible with the rescaled data for one particular propagation threshold.
- [Fig. 4a, §2, Fig. 6b] The choice of Δ0 as the time to reach 50% of nodes is not derived from the model; in the model, Δ0 should be the time within which a second miner must solve the puzzle for a fork to occur, i.e., the time by which the first block reaches the second successful miner, not a network percentile. The paper shows in Fig. 4a that using 50%, 90%, or 99% propagation times changes the predicted fork rate by up to an order of magnitude, and Fig. 6b shows that the implied HHI is sometimes negative, which the authors correctly attribute to Δ0 being too large. The authors should clarify the interpretation of Δ0 in Eq. (8) in terms of the peer-to-peer propagation process, and report how the conclusions change if a different propagation-time percentile or a fitted Δ0 is used. This is necessary to substantiate the 'comparable with empirical stale blocks rate' claim.
minor comments (5)
- [Eq. (5) and the preceding joint density] There is a sign error or typo in the exponent of the joint density before Eq. (5): as printed, e^{λ_i(t−t′)+Σ_k λ_k t′} does not integrate to Eqs. (5)–(6). The correct exponent should be e^{λ_i(t′−t)−Σ_k λ_k t′} (or an equivalent decaying form). Please fix this to make the derivation self-contained for readers.
- [Eq. (12), §4.1.5] The method-of-moments estimators for the truncated power-law parameters are stated as α = 1 − (m/s)^2 and β = m/s^2; the expression for α should be 1 − (m/s)^2 only if the variance is such that s > m, which holds here, but the notation is likely a typo for 1 − (m/s)^2. Please clarify the formula and its domain of validity.
- [§4.1.2] The fork rate is defined as the number of block heights with at least one stale or orphan block divided by the total number of blocks, but the term 'fork rate' is later used interchangeably with the probability that a block becomes a stale block. These are not the same quantity, and the distinction should be stated explicitly.
- [Fig. 4b, Fig. 5] The 90% confidence band around the historical fork-rate series is mentioned but its construction is not described. Please specify the source of uncertainty (e.g., Poisson sampling, resampling, or measurement noise) used to produce the shaded area.
- [§C.3.3 and Fig. 8/9] The 'truncated power law' in Eq. (24) is a Gamma-like density with an exponential cutoff, not a truncated power law in the sense of Burroughs and Tebbens [22]; please justify the naming or use a standard term such as 'power law with exponential cutoff.' Also, the text in §C.3.4 refers to Fig. 9 when describing the scenarios of zero miners, but the fork-rate results are in Fig. 8; please correct the cross-references.
Circularity Check
The fork-rate formula Eq. (8) is derived from independent inputs; the empirical validation is partly calibrated and self-confirming, and a minor non-load-bearing self-citation appears in the distributional rationale.
-
other
[Methods §4.1.2 (Forks) and Results §2 (Fig. 4b)]
"The bitcoin-data/stale-blocks is likely to under-report stale blocks due to its crowd-sourced nature: to reconcile it with other data sources, we adjust the computed fork rate to match the value of 0.41% reported by Gervais et al. [18] at the end of February 2016. This results in a rescaling of the fork rates by a factor of 1.476. ... We show in Fig. 4b that the model-predicted fork rate is largely consistent with the empirically estimated fork rate when Δ0 = Δ(50)0."
The empirical fork-rate series used as the benchmark is rescaled to hit a single external target (0.41% at Feb 2016), so it is not a purely observed validation series. The model input Δ0 is then selected among the 50/90/99 percentiles after seeing which yields agreement (Fig. 4b uses Δ0(50)). Thus the claim of empirical consistency is partly self-confirming: the comparison scale is anchored to a literature value and the propagation threshold is chosen post hoc, rather than being an out-of-sample test of Eq. (8). This does not make the derivation of Eq. (8) circular, as the hash-rate distribution and Δ0 are independent inputs, but it weakens the empirical validation.
full rationale
The central fork-rate formula, Eq. (8) ≈ Δ0·Λ·(1−HHI), is derived analytically from the joint distribution of the first two order statistics of N independent exponential mining times (Eqs. 1–6). The inputs N, {λi}, and Δ0 are measured independently from blockchain and network data; no parameter is fitted to fork rates. The derivation is therefore self-contained and not circular: the HHI dependence emerges from the exponential order statistics, not from a fit. The empirical comparison is partly softened by the rescaling of the fork-rate series to match a Gervais et al. value and by the post-hoc choice of Δ0(50) among three percentiles, which introduces an element of self-confirmation in the validation step. Additionally, the paper's Discussion acknowledges the strong synchronized-start assumption; this is a modeling limitation rather than circularity. Finally, the cited support for the log-normal distribution includes two self-citations ([16] and [21]), but these are not load-bearing because the main results hold across all considered distributions. Overall, the theoretical result is not reduced to its inputs, so the circularity score is low.
Assumptions & free parameters
free parameters (5)
- Exponential rate r (per period) =
e.g., 49,565 (2015-06); 19,159 (2023-12)
- Log-normal parameters μ, σ2 (per period) =
e.g., μ = -11.96, σ = 1.52 (2015-06)
- Truncated power-law parameters α, β (per period) =
e.g., α = 0.89, β = 5,518 (2015-06)
- Fork-rate rescaling factor =
1.476
- Propagation-time percentile used for headline comparison =
50% (median)
assumptions (6)
- domain assumption Mining times are exponentially distributed (Poisson arrivals)
- domain assumption All miners start mining the next block at the same time
- domain assumption Zero propagation delay within mining pools
- domain assumption Hash rates are independent across miners
- domain assumption Hash rates are constant within each 20,000-block period
- standard math Order statistics of independent exponential random variables
Cite this review
Pith. "Pith review of How the interplay between power concentration, competition, and propagation affects the resource efficiency of distributed ledgers." pith.science (2026). https://pith.science/paper/KFYWTPL7
@misc{pith2026241110249,
author = {Pith},
title = {Pith review of: How the interplay between power concentration, competition, and propagation affects the resource efficiency of distributed ledgers},
year = {2026},
howpublished = {\url{https://pith.science/paper/KFYWTPL7}},
note = {Machine review of arXiv:2411.10249}
}
read the original abstract
Forks in the Bitcoin network result from the natural competition in the blockchain's Proof-of-Work consensus protocol. Their frequency is a critical indicator for the efficiency of a distributed ledger as they can contribute to resource waste and network insecurity. We introduce a model for the estimation of natural fork rates in a network of heterogeneous miners as a function of their number, the distribution of hash rates and the block propagation time over the peer-to-peer infrastructure. Despite relatively simplistic assumptions, such as zero propagation delay within mining pools, the model predicts fork rates which are comparable with the empirical stale blocks rate. In the past decade, we observe a reduction in the number of mining pools approximately by a factor 3, and quantify its consequences for the fork rate, whilst showing the emergence of a truncated power-law distribution in hash rates, justified by a rich-get-richer effect constrained by global energy supply limits. We demonstrate, both empirically and with the aid of our quantitative model, that the ratio between the block propagation time and the mining time is a sufficiently accurate estimator of the fork rate, but also quantify its dependence on the heterogeneity of miner activities. We provide empirical and theoretical evidence that both hash rate concentration and lower block propagation time reduce fork rates in distributed ledgers. Our work introduces a robust mathematical setting for investigating power concentration and competition on a distributed network, for interpreting discrepancies in fork rates -- for example caused by selfish mining practices and asymmetric propagation times -- thus providing an effective tool for designing future and alternative scenarios for existing and new blockchain distributed mining systems.
Figures
Figures from the paper (7 more)
Reference graph
Works this paper leans on
-
[18]
On the Security and Performance of Proof of Work Blockchains
Arthur Gervais et al. “On the Security and Performance of Proof of Work Blockchains”. In:Proceed- ings of the 2016 ACM SIGSAC Conference on Computer and Communications Security. Vol. 24- 28-Octo. New York, NY, USA: ACM, Oct. 2016, pp. 3–16.isbn: 9781450341394. doi: 10.1145/ 2976749.2978341. url: https://dl.acm.org/doi/10.1145/2976749.2978341
arXiv 2016
-
[1]
Bitcoin: A Peer-to-Peer Electronic Cash System
Satoshi Nakamoto. “Bitcoin: A Peer-to-Peer Electronic Cash System”. In: (2008). url: https:// assets.pubpub.org/d8wct41f/31611263538139.pdf
-
[2]
Glenn M. Lilly. Device for and Method of One-way Cryptographic Hashing. Dec. 2004
work page 2004
-
[3]
Brian Arthur.Increasing Returns and Path Dependence in the Economy
W. Brian Arthur.Increasing Returns and Path Dependence in the Economy. University of Michigan Press, 1994, p. 201.isbn: 9780472022403
work page 1994
-
[4]
Bitcoin Security under Temporary Dishonest Majority
Georgia Avarikioti et al. “Bitcoin Security under Temporary Dishonest Majority”. In:Financial Cryptography and Data Security 2019 Proceedings. 2019, pp. 1–17
work page 2019
-
[5]
Information propagation in the Bitcoin network
Christian Decker and Roger Wattenhofer. “Information propagation in the Bitcoin network”. In: IEEE P2P Proceedings. IEEE, Sept. 2013, pp. 1–10.isbn: 978-1-4799-0515-7. doi: 10.1109/P2P. 2013.6688704. url: http://ieeexplore.ieee.org/document/6688704/
arXiv 2013
-
[6]
Ittay Eyal and Emin Gün Sirer. “Majority is not enough”. In:Communications of the ACM61.7 (June 2018), pp. 95–102.issn: 0001-0782. doi: 10.1145/3212998. url: https://dl.acm.org/doi/10. 1145/3212998
doi:10.1145/3212998 2018
-
[7]
Consensus formation on heterogeneous networks
Edoardo Fadda et al. “Consensus formation on heterogeneous networks”. In: EPJ Data Science 11.1 (Dec. 2022), p. 34. issn: 2193-1127. doi: 10.1140/epjds/s13688-022-00347-5. url: https: //epjdatascience.springeropen.com/articles/10.1140/epjds/s13688-022-00347-5
Show all 22 references
-
[8]
Short Paper: An Empirical Analysis of Blockchain Forks in Bitcoin
Till Neudecker and Hannes Hartenstein. “Short Paper: An Empirical Analysis of Blockchain Forks in Bitcoin”. In:Financial Cryptography and Data Security. 2019, pp. 84–92.doi: 10.1007/978-3- 030-32101-7{\_}6. url: http://link.springer.com/10.1007/978-3-030-32101-7_6
2019 doi
-
[9]
Performance modeling and analysis of the bitcoin inventory protocol
Yahya Shahsavari, Kaiwen Zhang, and Chamseddine Talhi. “Performance modeling and analysis of the bitcoin inventory protocol”. In:IEEE International Conference on Decentralized Applications and Infrastructures (DAPPCON). 2019, pp. 79–88. doi: 10.1109/DAPPCON.2019.00019. url: ht...
2019
- [10]
-
[11]
Unintentional forking analysis in wireless blockchain networks
Qilie Liu et al. “Unintentional forking analysis in wireless blockchain networks”. In:Digital Com- munications and Networks 7.3 (Aug. 2021), pp. 335–341. issn: 23528648. doi: 10.1016/j.dcan. 2020.12.005. url: https://linkinghub.elsevier.com/retrieve/pii/S2352864820302923
2021 doi
-
[12]
Majority is not enough: Bitcoin mining is vulnerable
Ittay Eyal and Emin Gün Sirer. “Majority is not enough: Bitcoin mining is vulnerable”. In:Inter- national conference on financial cryptography and data security. 2014, pp. 436–454
2014
-
[13]
Stubborn mining: Generalizing selfish mining and combining with an eclipse attack
Kartik Nayak et al. “Stubborn mining: Generalizing selfish mining and combining with an eclipse attack”. In:Proceedings - 2016 IEEE European Symposium on Security and Privacy, EURO S and P 2016 (May 2016), pp. 305–320.doi: 10.1109/EUROSP.2016.32
2016 doi
-
[14]
On the strategy and behavior of bitcoin mining with N-attackers
Hanqing Liu et al. “On the strategy and behavior of bitcoin mining with N-attackers”. In:ASIACCS 2018 - Proceedings of the 2018 ACM Asia Conference on Computer and Communications Security 12 (May 2018), pp. 357–368.doi: 10.1145/3196494.3196512. url: https://dl.acm.org/doi/10. ...
2018
-
[15]
Twisted by the Pools: Detection of Selfish Anomalies in Proof-of-Work Mining
Sheng-Nan Li, Carlo Campajola, and Claudio J. Tessone. “Twisted by the Pools: Detection of Selfish Anomalies in Proof-of-Work Mining”. In:arXiv preprint arXiv:2208.05748 (Aug. 2022). doi: 10.48550/arXiv.2208.05748. url: https://arxiv.org/abs/2208.05748
-
[16]
The Evolution Of Centralisation on Cryptocurrency Platforms
Carlo Campajola et al. “The Evolution Of Centralisation on Cryptocurrency Platforms”. In:arXiv preprint arXiv:2206.05081 (June 2022). url: https://arxiv.org/abs/2206.05081v2. 11
2022 arXiv
-
[17]
Blockchain Analysis of the Bitcoin Market
Igor Makarov and Antoinette Schoar. “Blockchain Analysis of the Bitcoin Market”. In: SSRN 3942181 (Oct. 2021). doi: 10.3386/W29396. url: https://www.nber.org/papers/w29396
2021 doi
-
[19]
A Brief History of Generative Models for Power Law and Lognormal Distributions
Michael Mitzenmacher. “A Brief History of Generative Models for Power Law and Lognormal Distributions”. In: Internet Mathematics 1.2 (2004), pp. 226–251. issn: 19449488. doi: 10.1080/ 15427951.2004.10129088. url: https://www.tandfonline.com/doi/abs/10.1080/15427951.2004. 10129088
2004
-
[20]
Heterogeneity- and homophily-induced vulnerability of a P2P network formation model: the IOTA auto-peering protocol
Yu Gao et al. “Heterogeneity- and homophily-induced vulnerability of a P2P network formation model: the IOTA auto-peering protocol”. In:arXiv preprint arXiv:2401.12633 (Jan. 2024). url: https://arxiv.org/abs/2401.12633v1
2024 arXiv
-
[21]
MicroVelocity: rethinking the Velocity of Money for digital currencies
Carlo Campajola, Marco D’Errico, and Claudio J. Tessone. “MicroVelocity: rethinking the Velocity of Money for digital currencies”. In: arXiv preprint arXiv:2201.13416 (Jan. 2022). url: https: //arxiv.org/abs/2201.13416v2
2022 arXiv
-
[22]
Upper-truncated power laws in natural systems
Stephen M. Burroughs and Sarah F. Tebbens. “Upper-truncated power laws in natural systems”. In: Pure and Applied Geophysics158.4 (2001), pp. 741–757.issn: 00334553. doi: 10.1007/pl00001202. url: https://link.springer.com/article/10.1007/PL00001202. 12 Supplementary Material A ...
2001 doi
Reviewed August 12, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.