What is "effective aid"?

The research questions of my dissertation will be:
What does constrain donors' change efforts at translating their officially stated commitments into effective aid outcomes?How can it be overcome?
I know donors have been busy discussing "more effective aid". But, "what is effective aid?" I assume that would be operationalised by measuring to what extent donors' intervention has improved livelihoods of targeted beneficiaries. However, that does not look straight forward at all... "How can we measure the improvement of livelihoods?" by income? by infant mortality rate? by unemployment rate??? or whatever. "How can we define 'target beneficiaries'?"
Shouldn't we consider secondary (indirect) impact considered to be brought by development intervention???
I am at the moment totally at a loss how to construct my argument in my dissertation... Possibly, I may pay attention to "process", that is, the ways how development interventions are being conducted, or what the primary stakeholders are learning because of those interventions. A point which is clear is that my analysis will put an emphasis on donors' perspectives. This would be due to my experience as one of the staffs of a donor agency, and something "sad" I felt while I engaged in my task... Development practitioners must have been motivated by something humanistic at least at the beginning. But, I saw large part of my colleagues get more and more inclined to rules rather than their own original motivation, feeling or anything lively. Practices of an organisation seem discrete from HQ, international donor community, to local levels. What I am taking seriously is not existing structural issues, but lack of something enthusiastic, or imagination about what other people are doing, and why.

Studying social science would provide me with opportunities to investigate enormously messy world of humanbeings... Of course, it is hard as well as exciting...