\section{Geographic heterogeneity}
\label{sec:geography}

Figure~\ref{fig:map} maps the coverage of the stage-one included records and of the extracted studies, and Table~\ref{tab:geography}
lists the countries contributing the most records and estimates. Coverage is broad in records (\nCountriesStageOne{} countries at
stage one) and narrower in extracted full texts (\nCountriesExtracted{} countries), because open-access availability is itself
unequal across publication venues and regions. Figure~\ref{fig:geo} shows the distribution of harmonised estimates by continent
for the six most-studied characteristic--family combinations. The living-area elasticity is centred between 0.5 and 0.8 on
every continent with at least five studies; the bedroom semi-elasticity is close to zero in North America, where living area is
almost always controlled, and larger in Asia and Europe, where room counts more often proxy for size; the age semi-elasticity is
negative everywhere with a wider dispersion in Asia, where samples mix new-build and resale apartments; and the premium of a
detached dwelling type varies from negative to large positive values within Europe, which reflects the diversity of reference
categories rather than a geographic law. The moderator analysis of Section~\ref{sec:methodological} tests the non-US indicator
formally: it is significant in \nSigNonus{} of \nTestedNonus{} models, raising the living-area semi-elasticity outside the United
States, and insignificant elsewhere. The honest summary of RQ3 is that geography matters through the composition of studies
(property types, specifications, units) more than through a detectable continental shift in implicit prices once those are
controlled, with the important caveat that Africa, South America and Oceania contribute too few studies for any contrast to be
powered.

\begin{figure}[H]
\centering
\includegraphics[width=\textwidth]{fig03_world_coverage.pdf}
\caption{Geographic coverage: stage-one included hedonic records (country from title and abstract) and extracted studies.}
\label{fig:map}
\end{figure}

\begin{table}[H]
\centering
\caption{Geographic distribution of the evidence (countries with the most stage-one included records)}
\label{tab:geography}
\small
\resizebox{0.8\textwidth}{!}{\input{tables/tab02_geography}}
\end{table}

\begin{figure}[H]
\centering
\includegraphics[width=\textwidth]{fig08_geographic_heterogeneity.pdf}
\caption{Distribution of harmonised estimates by continent for the six most-studied characteristic--family combinations
(boxes: interquartile range; line: median; whiskers: 1.5 IQR; $k$ = studies).}
\label{fig:geo}
\end{figure}