What constitutes a "manager or supervisor" in a criminal case?

Section 3B1.1(b) of the Guidelines requires a three-step increase in offense level if "the defendant was a manager or supervisor (but not an organizer or leader) and the criminal activity involved five or more participants or was otherwise extensive...." Guidelines 3B1.1(b). A defendant may properly be considered a manager or supervisor if he "exercise[d] some degree of control over others involved in the commission of the offense ... or play[ed] a significant role in the decision to recruit or to supervise lower-level participants." Ellerby v. United States, 187 F.3d at 259 (internal quotation marks omitted); see also Guidelines 3B1.1 Application Note 4.