Here's an answer that's quite similar, at first glance, to @Sigur's answer. It differs from Sigur's by (a) providing adjustments to make sure that the .
("dot", "period", "full stop") isn't misinterpreted as a sentence-ending punctuation mark, (b) placing the parentheses solely around the variable names, not their subscript terms, (c) providing for explicit italic corrections and, most importantly, (d) taking a more "LaTeX-y" approach to things, by which I mean separating meaning from form, by defining a macro called \vn
(short for "variable name") that's to be used to display variable names. In the code below, I've chosen the definition \newcommand\vn[1]{\textit{#1}}
. An advantage of such a setup is that if you ever, at some point in the future, decide that you'd rather display variable names using an upright rather than an italic font, all you'd need to do is change the definition of \vn
. In particular, you would not have to go and check each and every instance of \textit
in the document and decide whether it needs to be changed to \textrm
.
The following code also makes some spacing adjustments between \vn{democ}
and its associated subscript terms.

\documentclass{article}
\usepackage{amsmath}
\newcommand\vn[1]{\textit{#1\/}} % to display a variable name
%% note the italic correction provided by "\/"
\begin{document}
\begin{equation}
\begin{split}
\vn{democ}_{\mkern1.5mu i,t} &=
\alpha\, \vn{democ}_{\mkern1.5mu i,t-5} + \beta\, (\vn{students abroad})_{i,t-5} \\
&\quad +\gamma\, (\vn{democ.\ in receiving countries})_{i,t-5} \\
&\quad +\delta\, (\vn{students abroad})_{i,t-5}\, (\vn{democ.\ in receiving countries})_{i,t-5} \\
&\quad +(\vn{country fixed effects})_i + (\vn{time fixed effects})_t + \epsilon_{i,t}
\end{split}
\end{equation}
\end{document}
\text{}
fromamsmath
package. Otherwise, it is not a text, but a sequence of math variables.\mathit
rather than\textit
but never use the default math italic font for multi-letter identifiers, it is explictly designed with wide sidebearings so adjacent letters do not look like part of a ward but as a product of variables.\mathit
is set up for the math font setup as a fixed math alphabet font.\textit
is the current text italic font (so for example would be bold italic if the text font outside the math was bold) and it might be a completely different font set, by default they are both computer modern italic but math and texts fonts are separately specified and do not have to be the same.