NEWS

xtife 0.1.5

Alignment of the unbalanced-panel estimator with the reference methodology of Su, Wang and Wang (2025) doi:10.2139/ssrn.5177283, plus a related fix.

The nuclear-norm penalty grid is now c * max(N, T) for c in {0.01, 0.1, 1, 10} — the grid of Su, Wang and Wang (2025, footnote 12). Previously c * sqrt(max(N, T)).
The default initialisation of ife_unbalanced() is now init = "nnr" (the nuclear-norm-regularised consistent initial estimator, the first step of the reference two-step procedure). init = "ols" remains available as a faster warm start.
Fixed: a penalty exceeding the largest singular value shrank the low-rank component to exactly zero, making the singular-value- thresholding rule in ife_select_r_unb() degenerate (it could return r_hat = min(N, T)). Degenerate penalty candidates are now excluded, an all-degenerate grid errors informatively, and the SVT count guards against a zero first singular value.

ife_unbalanced() gains full additive fixed-effect support via force ("none", "unit", "time", "two-way"), estimated jointly with the factors by EM on the imputed panel; replaces the previous grand-mean centering, which was selection-biased under informative missingness.
Fixed the sign convention of the static bias correction (Bai 2009: corrected = raw − B/N − C/T) and the premultiplication of the Moon–Weidner dynamic bias-correction contributions.
Standard-error degrees of freedom account for additive fixed effects under force; factor space augmented with the additive effects for SE and bias-correction computations.
Four standard-error types for unbalanced panels: "standard", "robust" (HC1), "cluster" (by unit), "hac" (Bartlett kernel, bandwidth floor(2 * T^0.2)).
Documentation cites Su, Wang and Wang (2025) in standard author–year form throughout.