Via Andrew Leigh, a fascinating little piece of information:

This paper uses a new database on foreign aid to examine the
relationships among foreign aid, economic policies, and growth of per
capita GDP. In panel growth regressions for 56 developing countries and
six four-year periods (1970-93) the policies that have a large effect
on growth are fiscal surplus, inflation, and trade openness. We
construct an index of these three policies, interact it with foreign
aid, and instrument for both aid and aid interacted with policies. We
find that aid has a positive impact on growth in developing countries
with good fiscal, monetary, and trade policies. In the presence of poor
policies, on the other hand, aid has no positive effect on growth. This
result is robust in a variety of specifications that include or exclude
middle-income countries, include or exclude outliers, and treat
policies as exogenous or endogenous. We examine the determinants of
policy and find no evidence that aid has systematically affected
policies – either for good or for ill. We estimate an aid allocation
equation and show that any tendency for aid to reward good policies has
been overwhelmed by donors’ pursuit of their own strategic interests.
In a counterfactual we reallocate aid, reducing the role of donor
interests and increasing the importance of policy: such a reallocation
would have a large, positive effect on developing countries’ growth
rates.

Good policies first, the most important thing. Who would have thought it?