Signs declaring 'anti-Zionism is antisemitism' plastered with 'Free Palestine' in pair of incidents, with group representing anti-Zionist Jews claiming responsibility for one

Approximately 4,000 agencies do not participate in study, with 35 major US cities -- including New York, Los Angeles and Miami -- not submitting any data

Department says resignation unconnected to complaints he used position to push issues close to him, including preferential treatment for Zionist Organization of America