[Tex/LaTex] Weird spacing between some letters in math mode

Question

Input:

\begin{equation}
\begin{split}
democ_{i,t}={} & \alpha\,democ_{i,t-5} \quad+\quad 
\beta\,students\;abroad_{i,t-5} \quad+\quad \\ & 
\gamma\,democ.\;in\;receiving\;countries_{i,t-5} \quad+\quad\ \\ & 
\delta\,(students\;abroad_{i,t- 
5}*democ.\;in\;receiving\;countries_{i,t-5}) \quad+\quad \\ & 
country\;fixed\;effects_i \quad+\quad time\;fixed\;effects_t 
\quad+\quad \epsilon_{i,t}
\end{split}
\end{equation}

Output:

Why is there extra spacing between the f's in 'effects' when every other word is properly spaced? How do I fix it?

Answer 1

I propose this format (with \bigl( \bigr) if you wish):

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{aligned}
\textit{democ}_{i,t} &= 
\alpha\, (\textit{democ}_{i,t-5}) + \beta\, (\textit{students abroad}_{i,t-5}) \\ 
&\quad  + \gamma\, (\textit{democ. in receiving countries}_{i,t-5}) \\ 
&\quad  + \delta\, (\textit{students abroad}_{i,t- 5}) (\textit{democ. in receiving countries}_{i,t-5}) \\ 
&\quad  + \textit{country fixed effects}_i +  \textit{time fixed effects}_t + \epsilon_{i,t}
\end{aligned}
\end{equation}
\end{document}