The mayor's NATO point person, Lori Healey, estimates the Chicago summit cost at $55 million, much of which the federal government will likely cover. The scope of the protests is harder to predict. But a look back at recent international gatherings might provide some clues.

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  Deauville, France
May 2011 G8
Lisbon, Portugal
Nov 2010 NATO
Toronto, Canada
June 2010 G20/G8
Strasbourg, France, and Kehl, Germany
London, England
APR 2009 G20

Total cost of summit
$85 million N/A $858 million $147 million $30 million

4,000 to 7,000 30,000 Tens of thousands 17,000 5,000

100 42 1,090 N/A 122
SOURCES: NATO, The New York Times, Herald Sun, Belfast Telegraph, The Globe and Mail, Al Jazeera, Reuters, 2011 Canadian House of Commons Report, CBC News, Der Spiegel, Die Welt, BBC News