\section{Limitations}\label{sec:limits}

\begin{enumerate}
\item \textbf{Posted, not paid, prices.} We observe catalogue and circular prices, not transactions, quantities or expenditure weights. Nothing here is a welfare measure or a consumer price index.
\item \textbf{Eleven weeks.} The window is too short for the registered minimum durations of H3 (26 weeks) and of the index validation against official statistics (52 weeks); seasonal patterns are invisible; the promotion recurrence interval is right-censored.
\item \textbf{No store identifiers.} Storefront prices are mixtures over unknown stores; circulars are for one Montréal postal code; the ``nearby stores'' part of H4, the travel-cost part of H6 and QGPAI component 5 cannot be computed. The prospective design in Section~\ref{sec:repro} addresses this.
\item \textbf{Inferred promotion states.} Regular prices are not historised for storefronts, so promotion states rest on a 10\%-below-trailing-mode rule validated only against the current on-sale flag (agreement 0.90) and the circular depth distribution. Small reductions and loyalty prices are classified as regular.
\item \textbf{Matching coverage and error.} Exactly matched products are 11\% of listings and 93\% of matched group-weeks are within-company pairs. Tier~B carries an estimated 7\% rate of hidden-variant false matches on UPC ground truth; the reviewed sample is small (60 pairs per tier) and its final labels were set by the research operator rather than by independent human coders; PI adjudication is pending.
\item \textbf{Assortment coverage.} The connectors of the large chains read a subset of aisles; Giant Tiger, Epipresto, La Boîte à Grains and Nuvo are read exhaustively. Market-level statistics are therefore not representative of the grocery basket's expenditure shares.
\item \textbf{Package changes unobserved.} Size labels are stored as current state; within-listing downsizing cannot be detected.
\item \textbf{Weak external benchmark.} Two monthly CPI observations overlap the window.
\item \textbf{Analytic amendments.} Three post-registration amendments (A-001 to A-003) were required; each is logged with the preregistered alternative.
\end{enumerate}