The truth conditions of "know whether" reports - statements that feature the matrix predicate "know" embedding a polar question - have not been a matter of controversy (Karttunen 1977, Lewis 1982, Groenendijk and Stokhof 1982). What does not seem to have been observed, however, is that negated "know whether" reports are judged to convey more information about the agent's beliefs than received wisdom leads one to expect. For example, "Aisha doesn't know whether Ben is Canadian" is expected to merely convey that Aisha does not know the true answer to the embedded question, but it is actually understood to more specifically convey that Aisha is unopinionated about which answer to the embedded question is true. We will examine the prospects of relating such agent ignorance implications of negated "know whether" reports to speaker ignorance implications that have been described for both affirmative and negative "know whether" reports (Eckardt 2007, Egré 2008). We show that both types of ignorance implications are amenable to a derivation as quantity implicatures under neo-Gricean assumptions. However, we also find that,
surprisingly, agent ignorance inferences are more pervasive than the corresponding speaker ignorance implications, even though the neo-Gricean account would at best be consistent with the opposite pattern. This suggests that agent ignorance implications of negative "know whether" reports are not in fact Gricean inferences, but part of the conventional meaning of such sentences.