“The density of settlement of economists over the whole empire of economic science is very uneven, with a few areas of modest size holding the bulk of the population.” (Herbert A. Simon).

Density means the quality or state of being dense.
Fluidity means the physical property of a substance that enables it to flow.

“Communication can’t always follow the top-down model. With the fluidity of information in business today, leaders need to be masterful listeners; they need to be able to receive as well as send.” (Joseph Badaracco).