Stiglitz on Aid and Growth

Sometimes I do not understand how Joseph Stiglitz's mind operates.

In any case, not much weight should be given to the IMF's statistical studies of the impact of foreign aid on growth. Different studies, with different countries, different techniques and different years, yield markedly different results. One set of studies, for instance, showed that aid does make a difference in countries with good governance and sound macroeconomic policies.

If I understand this correctly, the studies that estimate the impact of foreign aid on economic growth do not yield a robust conclusion (This coincides with my reading of the literature).  It all depends on the sample, technique, etc.  So what does Stiglitz conclude from these results.

More debt relief - encompassing more countries - is needed, but debt relief should be viewed as just a start. As Britain itself has pointed out, developing countries need more assistance and a fairer international trade regime.

I have no idea how this follows.