Subfigures in latex never shrinks to be on one row (pfd file)

Question

I'm trying to adjust two subfigures into one row. This is my code:

\begin{figure}[ht]
    \centering
\caption{Migration rates and nightlights in Albania in 1992-1995}
    
 
         \begin{subfigure}[a]{0.3\textwidth}
   
           \caption{Emigration rate before 1995 at the municipality level}
         \label{fig: migration_rate}
    \includegraphics[width=\linewidth, trim = 5cm 0cm 5cm 0cm, clip]{Figures/migration_rate.pdf}
   
    
    \end{subfigure}
  
     \begin{subfigure}[b]{0.3\textwidth}
      \caption{Night luminosity in 1992}
     \label{fig: nighlights}
    \includegraphics[width=\linewidth, trim = 5cm 0cm 5cm 0cm, clip]{Figures/nightlight.pdf}
   
    
    \end{subfigure}


     \caption*{\footnotesize{\textbf{Notes}:}}.
     
    
     \end{figure}


    

enter image description here

Even if I shrink the subfigure to tiny size (for example {0.01\textwidth}), the two always appear in one column. I have deep blank space on the left and right of both figures that I have tried to trim. Including or excluding "trim" does not change much.

How do I get the two into one row?

Thank you!