Statistics Canada celebrated a historic response rate to the 2016 census, but the agency is still dealing with a few holdouts.

The Globe and Mail has learned that 347 letters were sent last month to individuals who had not yet completed the 2016 census (202 for the short form and 145 for the long form). That is about in line with 331 letters that were sent after the 2011 census, when only the short form was mandatory.

Restoring the mandatory long-form census was one of the first official acts of the new Liberal government last year. The quick decision allowed Statistics Canada to shift gears in time for the 2016 survey, which is now complete. The agency has said it received a response rate of 98.4 per cent, including 97.8 per cent for the long-form census, which does not go out to all households.

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Statistics Canada's chief statistician, Wayne Smith, announced his resignation on Sept. 19 as a protest against information technology issues that he said were compromising the agency's independence. Mr. Smith sent the 347 compliance letters on Aug. 19, and the letters give a deadline of Sept. 9.

"Anyone convicted of an offence under the Statistics Act is liable to punishment as set out in the Statistics Act," the compliance letters stated.

The act says a person found guilty could face a fine of up to $500, up to three months in jail, or both.

How to manage these files is now an issue for Mr. Smith's replacement, Anil Arora.

In response to questions, Statistics Canada provided The Globe with the number of letters sent but did not say how many of the 347 individuals have complied.

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The next step for Statistics Canada will be to decide whether to refer any cases to the Public Prosecution Service of Canada. That office would then decide independently of Statistics Canada whether to prosecute a case.

Philip Cross, a former chief economic analyst at Statistics Canada who is now with the Macdonald-Laurier Institute, said the number of people who have not yet filled out the census is surprisingly low. Mr. Cross said the public debate in recent years over the importance of census data is likely a factor. He also noted that the 2016 census came with strongly worded warnings about the need to comply.

"I'm surprised that such a heavy-handed tactic worked, but it worked," he said. "What we don't know is whether people filled it out accurately."

In 2006, when both the long- and short-form census were mandatory, 64 cases were referred to the PPSC by Statistics Canada, which led to 52 charges and 12 cases that ended with a guilty verdict. In 2011, when the short form was mandatory but the Conservative government replaced the long form with a voluntary household survey, 54 cases were referred to PPSC, 48 charges were laid and 15 guilty verdicts were reached.

A spokesperson for Statistics Canada said that when charges are laid, the court sometimes asks the person to complete the census and the issue can be resolved.

Some individuals have carried on with the process, attracting media attention along the way.

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In 2014, a Toronto judge handed a conditional discharge to Janet Churnin, then 79, for refusing to fill out the mandatory census in 2011.

Ms. Churnin was sentenced to 50 hours of community service. A year earlier, Audrey Tobias, then 89, was found not guilty in a Toronto court, even though she refused to fill out the 2011 census, because the judge said conflicting testimony left doubt about her intent at the time.