arXiv subjects

Junnan He

Publications and source records attributed to Junnan He.

5 recordsLinked to original sources

arXiv2026

Ridge Estimation of High Dimensional Two-Way Fixed Effect Regression

We study a ridge estimator for the high-dimensional two-way fixed effect regression model with a sparse bipartite network. We develop concentration inequalities showing that when the ridge parameters increase as the log of the network size, the bias, and the variance-covariance matrix of the vector of estimated fixed effects converge to deterministic equivalents that depend only on the expected network. We provide simulations and an application using administrative data on wages for worker-firm matches.

econ.EM↗

arXiv2025

Getting There and Getting In: How Mobility and Sorting Keep Women out of Top Startup Accelerators

Startup accelerators are a leading gateway to venture capital, but top programs often require founders to relocate to a venture hub. From a hand-collected census of U.S. accelerator startups (2008-2011) followed for five years, we estimate a two-sided matching model that separates two channels behind the gender funding gap, geographic mobility and sorting across accelerator tiers. Women raise about 60% less than men over five years; the gap concentrates among non-relocating women, is largest at active-childrearing ages, and vanishes for relocators, while the mobility cost is near zero for men. Removing mobility frictions raises women's match quality but not their tier; reaching the high-funding top tier also requires removing the sorting disadvantage that women face. The 2012 JOBS Act eased the legal barrier and capacity grew tenfold, yet the U.S. VC dollar gap still tripled (2011-2020): closing it needs mobility, sorting, and capacity together.

econ.GN↗

arXiv2024

Capacity, Technology Portfolios, and the Paradox of Concentration

Does limiting the largest firm's capacity always lower prices? We model firms competing in supply schedules with multiple technologies, each with constant marginal cost up to capacity. In a tractable model, in which capacity and technological efficiency coexist as distinct sources of market power, we find that when the largest firm leads by efficiency, a small transfer of higher-cost capacity to the leader raises concentration yet lowers prices, contrary to standard antitrust intuition. Larger transfers raise prices, restoring standard intuition and tracing a non-monotone price-concentration relation. We prove existence and uniqueness of equilibrium, derive closed-form conditions for when transfers raise or lower prices, and extend the results to other oligopoly models. Evidence from Colombia's wholesale electricity market, where weather shocks shift hydropower capacity across technology-diversified firms, supports the pattern. Counterfactual transfers lower prices up to 30% in the least concentrated markets. We draw implications for capacity caps, divestitures, and mergers.

econ.GN↗

arXiv2023

Misspecified Model Estimation and Its Impact on Predictions

We study a linear statistical model where outcomes depend on regressors with fixed population coefficients and observation-specific latent coefficients, along with measurement errors. A decision-maker estimates population coefficients and uses the estimates to predict the latent coefficients for a given observation. We analyze how misspecification of some population coefficients distorts predictions, investigating comparative statics with respect to: (1) residual information in regressors associated with misspecified coefficients after projecting out those associated with free coefficients, (2) alignment between misspecification vector and latent-to-coefficient mapping. Applications include employee rating with unconscious bias and LLM-mediated consumer research.

econ.TH↗

arXiv2012

An alternative definition for the Conley relation

In the theory of dynamics of closed relations on compact Hausdorff spaces, the definition for the Conley relation $f^Ω$ of an iterated closed relation $f$ is nontrivial. This paper establishes a new equivalent definition for $f^Ω$, and discusses its interpretation.

math.DS↗