Measuring the Arrow of Time: Identification, Estimation, and Inference for Directional Structure in Multivariate Time Series
This study addresses the challenge of accurately identifying directional lead-lag relationships among variables in multivariate time series. It proposes a novel framework grounded in temporal irreversibility, rigorously defining directionality as behavioral asymmetry under time reversal. Central to this approach is the introduction of a circulation matrix derived from lagged covariances as the core measure of directionality. The methodology incorporates an unbiased estimator, cross-fitting debiasing, delete-block jackknife standard errors, and an exact randomization test under a block-wise null hypothesis, with extensions to nonlinear settings. Evaluated on four simulated systems with known directional structures, the proposed method substantially outperforms conventional approaches—including correlation networks, Granger causality, and transfer entropy—demonstrating markedly reduced misidentification of directional relationships.