The term cluster evaluation was coined in 1988 by W. K. Kellogg Foundation staff in an evaluation of a foundation-funded initiative; the concept was further developed and the technique practiced by Kellogg Foundation evaluation consultants and other practitioners in the evaluation community. A cluster is defined as a strategic collection of grants exploring or developing new approaches to an issue related to program area issues or strategy, with moderate focus on sustainability. Although there is probably not a single, comprehensive definition of cluster evaluation that is agreed on by all who are familiar with this type of evaluation, various evaluators have pointed out several basic characteristics:

1. It seeks to determine impact through aggregating outcomes from multiple sites or projects, whereas multisite evaluation seeks to determine ...