SCUL: California (Proposition 99) vs hollina/scul ================================================= .. currentmodule:: mlsynth This page documents the verification of mlsynth's :doc:`../scul` estimator against the authors' reference R package (`hollina/scul `_, Hollingsworth & Wing 2022). Cross-validation -- California (Proposition 99) ----------------------------------------------- On the cigarette panel shipped with the reference package (California plus 38 donor states, 28 years, treatment from the 19th period), SCUL builds the synthetic control as a rolling-origin cross-validated lasso of California's pre-treatment cigarette sales on a 76-column multi-type donor pool -- every donor state's per-capita sales and its retail price. mlsynth, fed the identical panel, reproduces the authors' ``SCUL()`` value-for-value: .. list-table:: :header-rows: 1 :widths: 34 22 22 18 * - Quantity - mlsynth - ``hollina/scul`` - abs. diff * - cross-validation penalty (median) - :math:`0.02121478` - :math:`0.02121478` - :math:`0` * - ATT (post-1988 mean, packs) - :math:`-13.171` - :math:`-13.306` - :math:`0.135` * - Cohen's D (pre-fit) - :math:`0.0137` - :math:`0.0160` - :math:`0.0023` The rolling-origin cross-validation penalty matches ``glmnet`` to ten digits -- the selection procedure ports exactly. The small ATT difference is not a method difference: the lasso solution is unique for continuously distributed donors [TIBSHIRANI2013]_, and ``glmnet``'s default convergence threshold slightly under-converges this correlated, high-dimensional (donors > pre-periods) problem. mlsynth solves the same penalty *exactly* (the Langlois & Darbon [LangloisDarbon2025]_ differential-inclusion homotopy, no convergence tolerance) and lands on the unique optimum; when ``glmnet`` is run to a tight threshold, the two agree on the donor support and on the weights to within :math:`10^{-5}`. The case runs the R package live and asserts the penalty matches bit-for-bit and the ATT and synthetic series agree to solver tolerance. Durable case ``scul_prop99`` (skips gracefully when ``Rscript`` or ``glmnet`` is unavailable); the committed side-by-side table is ``benchmarks/reference/scul_prop99/comparison.csv``.