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% Figure: Main Result
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\begin{figure}[htbp]
  \centering
  % --- Replace placeholder with actual figure file ---
  % \includegraphics[width=0.85\textwidth]{figures/main_result.pdf}
  %
  % Placeholder box (remove when replacing with actual figure)
  \fbox{\parbox{0.85\textwidth}{\centering\vspace{4cm}
    \textit{[Insert figure here: figures/main\_result.pdf]}
  \vspace{4cm}}}
  %
  \caption{Main Result --- Effect of $X$ on $Y$ Over Time}
  \label{fig:main_result}
  \begin{minipage}{0.85\textwidth}
    \vspace{0.3cm}
    \footnotesize\textit{Notes:} This figure plots \ldots{} over the sample period January~1990 to December~2023. The solid line represents \ldots{} The shaded area indicates the 95\% confidence interval. The dashed vertical line marks \ldots{}
  \end{minipage}
\end{figure}