The census form asked if each citizen was bilingual, able to speak both French and English. The same question has been asked for years on the census forms, and the number of Canadians who claimed to be bilingual has constantly increased throughout the years. The 2006 census, however, reported a lower number than before, which seems unlikely.
The probable cause is an anonymous email message written in French that circulated widely just before the census forms were mailed. The email message encouraged French-speaking Canadians to claim to be unable to speak English under the mistaken belief that the Canadian government might reduce services in French if more citizens were bilingual. Government officials have questioned the accuracy of the claims in the anonymous email message.
Statistics Canada has since taken the unusual step of posting a message on its web site to caution users that the 2006 data on bilingualism may not be reliable.
My thanks to Doug Cooper for telling me about this story.