There is a malicious and perverse relationship between the force of NGOs and the weakness of the Haitian state.That is Ricardo Seitenfus, the Brazilian head of the Organization of American States mission to Haiti during the 2010 earthquake - quoted by Acemoglu and Robinson.
This is the real challenge to aid project impact evaluations, whether randomised or not, and is really the key argument made by the critics from Bauer to Easterly to Moyo.
What isn't clear to me is how we should expect the impact of NGO activity on state strength to vary by the effectiveness of the project. Does the measured impact of the project on individuals have any relationship with the impact of the project on broader governance? It's at least plausible that a very effective health intervention (measured by outcomes for individuals) could also be effective in building state capacity for service delivery. Or on the contrary, the same measured improvement in outcomes for individuals could be consistent with undermining state capacity, by encouraging the state to spend less on health and more on other goodies, and also by poaching the best staff from the government into the NGO sector. Tricky.
Answers / more data sources on a postcard.