If donors and nonprofits felt that they had to measure their results, might that not lead them to focus on limited sorts of things that could be measured precisely: administering vaccines, for instance, rather than attempting to improve over-all health; or counting missed days of school rather than evaluating student achievement? And what would happen to things that could not properly be measured at all, such as oppression, or justice? What about initiatives whose success could take decades to become evident, such as social movements or the erosion of cultural norms?
What Money Can Buy: Darren Walker and the Ford Foundation set out to conquer inequality, New Yorker, January 4, 2016 [An example of the clothes line paradox]