supports de support
\left(
Wide-eyed Wildebeest
\left(\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
D_{it} =
\begin{cases}
1 & \text{if bank $i$ issues ABs at time $t$}\\
2 & \text{if bank $i$ issues CBs at time $t$}\\
0 & \text{otherwise}
\end{cases}
\end{equation}
\end{document}