In a June 2006 speech, then-Undersecretary of State Robert Joseph claimed that between April 2005 and April 2006 the United States had cooperated with other PSI participants on "roughly two dozen" occasions to prevent transfers of concern; and in May 2005 Ulrik Federspiel, Denmark’s ambassador to the United States, asserted that "the shipment of missiles has fallen significantly in the lifetime of PSI." However, references such as these provide no actual information on or evidence of interdictions which have occurred, leaving critics to remain skeptical of such numbers or of any "metrics" that prove the effectiveness of the initiative.