Albany Law professor Meredith R. Miller and graduate Grace Ann Porter examine the growing circuit split over the evidentiary standard courts must apply when deciding whether to authorize notice to potential opt-in plaintiffs in FLSA collective actions, tracing the diverging approaches of the Fifth, Sixth, Seventh, Second, and Ninth Circuits. Professor Miller and Ms. Porter argue that the emerging trend toward heightened scrutiny at the certification stage will practically narrow workers' ability to pursue collective wage and hour claims, because requiring plaintiffs to produce more substantial evidence before discovery both suppresses opt-in participation and creates a circular barrier to gathering the very evidence needed to establish similarity.