“…Recent studies have shown that machine-learning tools can be useful for principled variable selection (Goller, Lechner, Moczall, & Wolff, 2020;B. K. Lee, Lessler, & Stuart, 2010;Urminsky, Hansen, & Chernozhukov, 2016) and we show that our results are robust to a range of specifications, as suggested by Angrist and Frandsen (2019). We take caution in interpreting the treatment effect of the standard grant amount, given the strong unconfoundedness assumption required for identification.…”