1\documentclass{article}
2\usepackage{amsmath}
3\begin{document}
4\begin{equation}
5 D_{it} =
6 \begin{cases}
7 1 & \text{if bank $i$ issues ABs at time $t$}\\
8 2 & \text{if bank $i$ issues CBs at time $t$}\\
9 0 & \text{otherwise}
10 \end{cases}
11\end{equation}
12\end{document}