Econometrica

Journal Of The Econometric Society

An International Society for the Advancement of Economic
Theory in its Relation to Statistics and Mathematics

Edited by: Guido W. Imbens • Print ISSN: 0012-9682 • Online ISSN: 1468-0262

Econometrica: Nov, 2024, Volume 92, Issue 6

Sparse Network Asymptotics for Logistic Regression under Possible Misspecification

https://doi.org/10.3982/ECTA19051
p. 1837-1868

Bryan S. Graham

Consider a bipartite network where N consumers choose to buy or not to buy M different products. This paper considers the properties of the logit fit of the N × M array of “i‐buys‐j” purchase decisions, , onto a vector of known functions of consumer and product attributes under asymptotic sequences where (i) both N and M grow large, (ii) the average number of products purchased per consumer is finite in the limit, (iii) there exists dependence across elements in the same row or same column of Y (i.e., dyadic dependence), and (iv) the true conditional probability of making a purchase may, or may not, take the assumed logit form. Condition (ii) implies that the limiting network of purchases is sparse: only a vanishing fraction of all possible purchases are actually made. Under sparse network asymptotics, I show that the parameter indexing the logit approximation solves a particular Kullback–Leibler Information Criterion (KLIC) minimization problem (defined with respect to a certain Poisson population). This finding provides a simple characterization of the logit pseudo‐true parameter under general misspecification (analogous to a (mean squared error (MSE) minimizing) linear predictor approximation of a general conditional expectation function (CEF)). With respect to sampling theory, sparseness implies that the first and last terms in an extended Hoeffding‐type variance decomposition of the score of the logit pseudo composite log‐likelihood are of equal order. In contrast, under dense network asymptotics, the last term is asymptotically negligible. Asymptotic normality of the logistic regression coefficients is shown using a martingale central limit theorem (CLT) for triangular arrays. Unlike in the dense case, the normality result derived here also holds under degeneracy of the network graphon. Relatedly, when there “happens to be” no dyadic dependence in the data set in hand, it specializes to recently derived results on the behavior of logistic regression with rare events and i.i.d. data. Simulation results suggest that sparse network asymptotics better approximate the finite network distribution of the logit estimator. A short empirical illustration, and additional calibrated Monte Carlo experiments, further illustrate the main theoretical ideas.


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Supplemental Material

Supplement to "Sparse Network Asymptotics for Logistic Regression under Possible Misspecification"

Bryan S. Graham

In this supplemental web appendix I describe the variance estimators used in the Monte Carlo experiments reported in the main text. Graham (2020a) and Graham (2020b) both discuss variance estimation under dyadic dependence and provide references to the primary literature. Equation numbering continues in sequence with that established in the main paper.

Supplement to "Sparse Network Asymptotics for Logistic Regression under Possible Misspecification"

Bryan S. Graham

The replication package for this paper is available at https://doi.org/10.5281/zenodo.12811612. The Journal checked the data and codes included in the package for their ability to reproduce the results in the paper and approved online appendices.

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