The relationship between e-mail activity and hierarchical level is striking; the average executive (members of the top four salary bands) in our sample sent and received more than twice as many e-mails as the average middle manager who, in turn, sent and received more than twice as many as the average rank-and-file employee. Likewise, executives communicated with many more partners than middle managers or rank-and-file employees and their e-mails were substantially more dispersed across business unit, function, and office boundaries.

—HBS Paper on Communication & Coordination