REVIEW 3 major objections 8 minor 24 references
What Makes a Peer? Valuation-Anchored Similarity in Private Markets
T0 review · 3 major / 8 minor · reviewed 2026-08-16 · deepseek-v4-flash
Pith's one-line read Private-company peers are best defined by a valuation-trained tree ensemble: importance-weighted leaf co-occurrences form a similarity metric that improves k-NN valuation over Euclidean, Gower, and text-embedding baselines in the…
desk verdict A competent application of known tree-proximity methods to private-market peer identification, but the headline improvement claim is thinner than the abstract suggests and needs stronger empirical support. 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 central object is the tree-importance-weighted leaf-node co-occurrence similarity computed from an ensemble of gradient-boosted trees trained on log post-money valuation. For two companies $X_1$ and $X_2$, with $Z_{1,t}$ and $Z_{2,t}$ their terminal leaves in tree $t$, the similarity is $S(X_1,X_2)=\sum_t w_t\,\mathbb{I}[Z_{1,t}=Z_{2,t}]$, where $w_t$ is the normalized absolute reduction in training loss contributed by tree $t$; dissimilarity is $1-S(X_1,X_2)$. This turns the ensemble's splits into a pairwise geometry: firms are peers when valuation-relevant feature interactions repeatedly route them together, and the tree-boosting algorithm's handling of high-cardinality categorical variables and missing values makes the learned partitions feasible on sparse private-market data.
What would settle it
Train the identical ensemble and leaf-co-occurrence similarity on the subset of companies whose post-money valuations were directly observed, hold out the derived-valuation companies, and compare k-NN MAE and RMSE against the Euclidean, Gower, and text-embedding baselines; if the learned metric no longer dominates, or if nearest neighbors cluster by valuation-source type, the central claim is falsified.
Extended reading notes
Core claim
The central claim is that company similarity in private markets is better modeled as an output of supervised valuation learning than as a static feature distance. After fitting a gradient-boosted tree model to log post-money valuation, the authors define the similarity of two companies as the importance-weighted frequency with which both are routed to the same terminal leaf across the ensemble; weights are each tree's absolute reduction in training loss. The complement of this score is a bounded pairwise dissimilarity that is symmetric but not necessarily metric. Using about 53,000 valuation targets drawn from a roughly 270,000-company global universe, the paper reports that k-nearest-neighbor valuation estimates built on the learned metric have lower MAE and RMSE than k-NN built on Euclidean, Gower, or text-embedding cosine distances in the evaluated industry groups, and that the neighborhoods are explainable through Shapley-value feature attributions.
Load-bearing premise
The method assumes that the 53,000 valuations used for training are economically comparable even when some are directly reported and some are reconstructed from deal terms or enterprise values; if reconstruction noise is substantial, the learned peer groups may reflect how valuations were computed rather than why companies are economic peers.
Editorial extensions
If this is right
- k-nearest-neighbor valuation built on the learned similarity achieves lower MAE and RMSE than k-NN built on Euclidean, Gower, or text-embedding distances in the evaluated industry groups, without reusing the ensemble's own point predictions.
- The same learned similarity matrix can support sourcing, benchmarking, and concentration risk analysis: firms that share valuation drivers appear as neighbors even when conventional sector or geography filters would separate them.
- Because the similarity derives from a fixed trained ensemble, new companies can be projected into the same leaf-co-occurrence geometry, so peer relationships remain explainable by the features that drive the splits.
- Valuation uncertainty and peer structure can be reported coherently from one fitted model, since conformal prediction intervals and the similarity matrix are both outputs of the same ensemble.
Reading between the lines
- An implication the authors leave implicit is that the same importance-weighted leaf co-occurrence construction transfers to any scarce-outcome private-market target, such as private-credit pricing or exit likelihood, whenever the target variable defines what economic peerhood should mean.
- A testable diagnostic is to train the identical pipeline on only the directly observed post-money valuations and check whether the k-NN gains persist; if the metric no longer beats the baselines, the reported improvement is driven by construction patterns in derived valuation targets rather than economic content.
- Because the training snapshot spans nearly fifty years with recency weighting, the learned geometry likely drifts with market conditions; a natural extension is to re-estimate the ensemble on rolling windows and compare k-NN error across vintages.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes a supervised similarity-learning framework for private-market peer identification. The authors train a CatBoost gradient-boosted tree model on log post-money valuations of roughly 53,000 private companies and define pairwise company similarity as the tree-importance-weighted leaf-node co-occurrence frequency across the ensemble (Eqs. 1-6). They evaluate the learned dissimilarity in k-NN valuation tasks against Euclidean, Gower, and MPNet-embedding cosine baselines, reporting consistently lower MAE/RMSE in Financial Services, and also report SHAP-based and neighborhood-consistency analyses. The central claim is that the valuation-anchored similarity improves downstream k-NN valuation accuracy in the evaluated industry groups while retaining interpretability.
Significance. If the central claim holds, the framework would be a practically useful and commercially relevant extension of tree-proximity methods to private-market equity, and the paper would provide a concrete, explainable alternative to coarse-rule peer selection. The paper builds on established techniques (CatBoost, leaf-node co-occurrence, conformal prediction, SHAP) rather than introducing new theory, but the application domain and the explicit construction of a reusable pairwise similarity matrix are of potential interest to q-fin audiences. Strengths: the framework is clearly specified in closed form; the paper is candid about some limitations (dissimilarity not a metric, evaluation restricted to one industry group shown); the target construction and data provenance are described; and the design separates model fitting from test-set use. The empirical case is not yet convincing because results are shown for a single visible industry group with no uncertainty quantification.
major comments (3)
- [Section 6.2 and Abstract] The central claim of improved downstream k-NN valuation over Euclidean, Gower, and MPNet baselines is supported only by a single visible figure for Financial Services (Figure 4). No other industry groups, no numeric MAE/RMSE values, no standard errors, and no significance tests are reported, so the stated claim that improvements hold 'in the evaluated industry groups' cannot be assessed. Please report per-industry-group numeric results with error bars or paired tests across all evaluated groups, or narrow the claim accordingly.
- [Sections 3.4.1-3.4.2 and 6.2] The k-NN evaluation reuses as labels the same 53,000 log-valuation targets used to train the CatBoost model that defines the similarity metric (Eqs. 1-5). This is not a circular use of CatBoost predictions, but it does mean the comparison is supervised similarity against unsupervised baselines, which may largely reflect the value of supervision rather than the specific tree-weighting mechanism. To support the specific contribution, compare against an equally supervised baseline (e.g., random-forest proximity trained on the same target, or a metric learned by a deep metric-learning model), and report k-NN results with the tree-importance weights set to uniform to isolate the effect of Eq. 4.
- [Sections 2.1 and 4.1.1] The target variable is assembled from four heterogeneous sources - direct post-money valuation, enterprise value, deal size divided by acquisition percentage, and pre-money value plus deal size/offering amount - that are not economically equivalent. Because source type is correlated with deal type and stage, CatBoost can in principle pick up construction-recipe signatures rather than economic peerhood, and the learned similarity could then group companies by how their valuations were computed. Please report the share of targets from each source, test whether learned neighborhoods and k-NN gains are stable within source groups, and, ideally, retrain on direct post-money valuations only as a robustness check.
minor comments (8)
- [Section 3.4.1, Eqs. 3-4] The definition of training-loss improvement is a heuristic; note that because CatBoost uses ordered boosting with random permutations, training-loss differences are not variance-stabilized and the weights w_t can be dominated by noisy early iterations. A sentence acknowledging this and reporting the robustness of Eq. 5 to alternative weightings would strengthen the paper.
- [Section 4.1.2 and Table 2] The descriptions of multi-label concatenation and the cardinality for 'Region and City (4,816)' are unclear; specify how multi-label deal types are combined and how the region-and-city cardinality was counted.
- [Section 4.2.2] Recency-based sample weighting is described only qualitatively; provide the functional form of the weights or state explicitly that the weighting function is not disclosed.
- [Section 5.2] The retransformation scaling factors of 1.74, 5.06, and 2.19 by deal type are surprisingly large; briefly explain why 'Unspecified' transactions require a factor above 5 and whether these factors are stable across folds.
- [Section 5.1 and Table 4] The MAPE and MdAPE values are reported as percentages of log-space errors; clarify the definition because percentage errors are normally computed in level space, and the 0.05-0.07 values are not interpretable as conventional MAPE.
- [Figures 3 and 4] The figure captions are too terse; Figure 3 and Figure 4 should state the plotted quantity, the number of companies, and the error metric used.
- [Section 6.1] The claim that the learned metric shows 'mixed performance against Gower and Euclidean distances' on numerical features in Financial Services should be quantified or reconciled with the k-NN improvements in the same group.
- [References] The paper cites arXiv preprint and SSRN references without DOIs or access dates; the reference list should be completed before publication.
Circularity Check
No significant circularity: the similarity derivation is self-contained and the k-NN evaluation is out-of-sample.
full rationale
The similarity metric (Eq. 5) is derived from CatBoost leaf co-occurrences and tree weights defined in Eqs. 3-4 from training-loss reductions; this is a standard supervised distance-learning construction and is not defined in terms of the k-NN estimates it later supports. The k-NN benchmarking (Section 6.2) evaluates test companies against a fixed training reference set, with test valuations used only in final evaluation (Section 4.2.1), so the predictions are out-of-sample. The tree-importance weighting and leaf assignments are learned from the training valuations, but the evaluation does not reuse the CatBoost point predictions; using the same training labels to build a supervised kernel and as k-NN neighbor labels is the intended supervised-learning protocol, not an equation-level identity. Self-citations to prior tree-proximity and bond/municipal similarity papers are related-work context and are not load-bearing for the derivation. The heterogeneous construction of the target valuation and the comparison against unsupervised baselines are potential validity and interpretation concerns, but they do not make the derivation circular.
Assumptions & free parameters
free parameters (4)
- Recency-based training sample weights =
Not specified
- Log-space retransformation scaling factors by deal type =
Series: 1.74; Unspecified: 5.06; Other: 2.19
- Feature retention thresholds =
50% non-missing; zero-importance removal
- Target winsorization percentiles =
1st and 99th
assumptions (5)
- domain assumption Post-money valuation is a valid supervisory anchor for economic similarity.
- domain assumption Frequent co-occurrence in leaves of a valuation prediction tree implies economic peerhood.
- domain assumption CatBoost's ordered target statistics and ordered boosting eliminate target leakage into categorical encodings.
- domain assumption The most recent transaction's features represent firms on a comparable footing across a 1977-2025 sample.
- ad hoc to paper Training-loss improvement is the right measure of a tree's contribution to similarity.
Cite this review
Pith. "Pith review of What Makes a Peer? Valuation-Anchored Similarity in Private Markets." pith.science (2026). https://pith.science/paper/6JBL4QVJ
@misc{pith2026260812594,
author = {Pith},
title = {Pith review of: What Makes a Peer? Valuation-Anchored Similarity in Private Markets},
year = {2026},
howpublished = {\url{https://pith.science/paper/6JBL4QVJ}},
note = {Machine review of arXiv:2608.12594}
}
read the original abstract
As more investors contemplate private markets and contend with limited transparency, sparse disclosures, and infrequent transactions, identifying economically meaningful peer companies for comparison is a fundamental challenge for valuation, due diligence, portfolio construction, and risk management. We propose an ensemble tree-based supervised similarity learning framework that defines company similarity through the lens of market valuation rather than static feature matching or semantic descriptions. Specifically, we train a CatBoost gradient-boosted decision tree model on observed private company valuations and derive a valuation-aware similarity metric from importance-weighted leaf-node co-occurrences across the ensemble. The similarity metric captures shared valuation drivers while accommodating nonlinear relationships, mixed data types, and pervasive missing data common in private markets. Using a global private-market universe of approximately 270,000 companies, including more than 53,000 firms with observed or derivable post-money valuations spanning multiple industries, geographies, and deal stages, we demonstrate that the proposed similarity framework improves upon traditional distance-based and text-embedding-based approaches in downstream k-nearest-neighbor valuation tasks in the evaluated industry groups, while retaining case-based explainability.
Figures
Reference graph
Works this paper leans on
-
[1]
Private equity — global private markets report, February 2026
Alexander Edlich, Chris Llewellyn, Christopher Croke, Rahel Schneider, and Warren Teichner. Private equity — global private markets report, February 2026. URL https://www.mckinsey.com/industries/private-capital/our-insights/global- private-markets-report/private-equity. Accessed: May 2026
work page 2026
-
[2]
Aswath Damodaran.Damodaran on valuation: security analysis for investment and corporate finance. John Wiley & Sons, 2011
work page 2011
-
[3]
Supervised similarity learning for corporate bonds using random forest proximities
Jerinsh Jeyapaulraj, Dhruv Desai, Peter Chu, Dhagash Mehta, Stefano Pasquali, and Philip Sommer. Supervised similarity learning for corporate bonds using random forest proximities. InProceedings of the 3rd ACM International Conference on AI in Finance (ICAIF ’22), pages 411–419. ACM, 2022
work page 2022
-
[4]
Relative valuation with machine learning.Journal of Accounting Research, 61(1):329–376, 2023
Paul Geertsema and Helen Lu. Relative valuation with machine learning.Journal of Accounting Research, 61(1):329–376, 2023. doi: 10.1111/1475-679X.12464
-
[5]
Machine learning-based rela- tive valuation of municipal bonds
Preetha Saha, Jasmine Lyu, Dhruv Desai, Rishab Chauhan, Jerinsh Jeyapaulraj, Peter Chu, Philip Sommer, and Dhagash Mehta. Machine learning-based rela- tive valuation of municipal bonds. InProceedings of the 5th ACM International Conference on AI in Finance, pages 634–642, 2024
work page 2024
-
[6]
Joshua Rosaler, Luca Candelori, Vahagn Kirakosyan, Kharen Musaelian, Ryan Samson, Martin T Wells, Dhagash Mehta, and Stefano Pasquali. Supervised similarity for high-yield corporate bonds with quantum cognition machine learning.arXiv preprint arXiv:2502.01495, 2025. Frank et al. Figure 3: Financial Services (3.2k firms) Figure 4: k-NN Valuation by Neighbo...
arXiv 2025
-
[7]
McCarthy, Xiao Wang, and Kun Zhang
Ruling Zhang, Zengrui Tian, Killian J. McCarthy, Xiao Wang, and Kun Zhang. Application of machine learning techniques to predict entrepreneurial firm valuation.Journal of Forecasting, 42(2):402–417, 2023. doi: 10.1002/for.2913
-
[8]
Companykg: A large-scale heterogeneous graph for company similarity quantification
Lele Cao, Vilhelm von Ehrenheim, Mark Granroth-Wilding, Richard Anselmo Stahl, Andrew McCornack, Armin Catovic, and Dhiana Deva Cavalcanti Rocha. Companykg: A large-scale heterogeneous graph for company similarity quantification. InProceedings of the 30th ACM SIGKDD Conference on Knowledge Discovery and Data Mining, pages 4816–4827, 2024
work page 2024
Show all 24 references
-
[9]
Company similarity using large language models
Dimitrios Vamvourellis, Máté Tóth, Snigdha Bhagat, Dhruv Desai, Dhagash Mehta, and Stefano Pasquali. Company similarity using large language models. In2024 IEEE Symposium on Computational Intelligence for Financial Engineering and Economics (CIFEr), pages 1–9. IEEE, 2024
2024
-
[10]
A survey on metric learning for feature vectors and structured data.arXiv preprint arXiv:1306.6709, 2014
Aurélien Bellet, Amaury Habrard, and Marc Sebban. A survey on metric learning for feature vectors and structured data.arXiv preprint arXiv:1306.6709, 2014
2014 arXiv
-
[11]
Random forests.Machine Learning, 45(1):5–32, 2001
Leo Breiman. Random forests.Machine Learning, 45(1):5–32, 2001
2001
-
[12]
Geometry-and accuracy- preserving random forest proximities.IEEE Transactions on Pattern Analysis and Machine Intelligence, 45(9):10947–10959, 2023
Jake S Rhodes, Adele Cutler, and Kevin R Moon. Geometry-and accuracy- preserving random forest proximities.IEEE Transactions on Pattern Analysis and Machine Intelligence, 45(9):10947–10959, 2023
2023
-
[13]
Supervised similarity learning for corporate bonds using ran- dom forest proximities
Jerinsh Jeyapaulraj, Dhruv Desai, Dhagash Mehta, Peter Chu, Stefano Pasquali, and Philip Sommer. Supervised similarity learning for corporate bonds using ran- dom forest proximities. InProceedings of the Third ACM International Conference on AI in Finance, pages 411–419, 2022
2022
-
[14]
Distance metric learning with application to clustering with side-information
Eric W Xing, Michael I Jordan, Stuart J Russell, and Andrew Y Ng. Distance metric learning with application to clustering with side-information. InAdvances in Neural Information Processing Systems (NeurIPS), volume 15, pages 521–528, 2002
2002
-
[15]
Distance metric learning for large margin nearest neighbor classification.Journal of Machine Learning Research (JMLR), 10(2):207–244, 2009
Kilian Q Weinberger and Lawrence K Saul. Distance metric learning for large margin nearest neighbor classification.Journal of Machine Learning Research (JMLR), 10(2):207–244, 2009
2009
-
[16]
Lundberg, Gabriel G
Scott M. Lundberg, Gabriel G. Erion, Hugh Chen, et al. From local explanations to global understanding with explainable ai for trees.Nature Machine Intelligence, 2:56–67, 2020
2020
-
[17]
Clustering and similarity learning in financial markets: A tutorial for the practitioners
Dhagash Mehta, John RJ Thompson, Hoyoung Lee, and Yongjae Lee. Clustering and similarity learning in financial markets: A tutorial for the practitioners. A vailable at SSRN 5587353, 2025. What Makes a Peer? Valuation-Anchored Similarity in Private Markets
2025
-
[18]
Friedman
Jerome H. Friedman. Greedy function approximation: A gradient boosting machine.Annals of Statistics, 29(5):1189–1232, 2001
2001
-
[19]
Catboost: unbiased boosting with categorical features
Liudmila Prokhorenkova, Gleb Gusev, Aleksandr Vorobev, Anna Veronika Doro- gush, and Andrey Gulin. Catboost: unbiased boosting with categorical features. Advances in neural information processing systems, 31, 2018
2018
-
[20]
Optuna: A next-generation hyperparameter optimization framework
Takuya Akiba, Shotaro Sano, Toshihiko Yanase, Takeru Ohta, and Masanori Koyama. Optuna: A next-generation hyperparameter optimization framework. InProceedings of the 25th ACM SIGKDD international conference on knowledge discovery & data mining, pages 2623–2631, 2019
2019
-
[21]
A tutorial on conformal prediction.Journal of machine learning research, 9(3), 2008
Glenn Shafer and Vladimir Vovk. A tutorial on conformal prediction.Journal of machine learning research, 9(3), 2008
2008
-
[22]
Similarity-based conformal prediciton using random forest proximities
Mingshu Li, Dhruv Desai, Bhaskarjit Sarmah, Snigdha Bhagat, and Dhagash Mehta. Similarity-based conformal prediciton using random forest proximities. InProceedings of the 6th ACM International Conference on AI in Finance, pages 387–395, 2025
2025
-
[23]
A unified approach to interpreting model predictions
Scott M Lundberg and Su-In Lee. A unified approach to interpreting model predictions. In I. Guyon, U. V. Luxburg, S. Bengio, H. Wallach, R. Fergus, S. Vish- wanathan, and R. Garnett, editors,Advances in Neural Information Processing Sys- tems 30, pages 4765–4774. Curran Associ...
2017
-
[24]
Fast treeshap: Accelerating shap value computation for trees.arXiv preprint arXiv:2109.09847, 2021
Jilei Yang. Fast treeshap: Accelerating shap value computation for trees.arXiv preprint arXiv:2109.09847, 2021
2021 arXiv
Reviewed August 16, 2026 · model on record in the stance chip above.
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