Summary: When interacting with others you can be considerate of their preferences, for instance by being friendly or reliable. This normally has small positive direct effects. But, by improving your reputation or strengthening aspects of culture that make a community more cooperative, the positive indirect effects can be large.
In a previous post, Max suggested two key ways of thinking about diminishing returns: funding gaps and returns functions. He also set out two classes of considerations that are generally desirable in models: closeness of fit and clarity.
As organisations receive more funding, the value of extra funding changes. This is relevant for donation decisions. People have used various concepts to discuss this feature:
It is well known that an extra dollar is worth less when you have more money. This paper describes the way economists typically model that effect, using that to compare the effectiveness of different interventions. It takes remittances as a particular case study.