TODAY is World Statistics Day—an event you’ve probably never heard of, but which has special resonance in Canada, where one of the hottest political debates of recent months has involved number-crunching. The question of whether responses to the long form of the census, sent to a representative group every five years, should be voluntary or remain mandatory may seem rather technical. But it has pitted the country’s two largest provinces, Ontario and Quebec, against the minority Conservative government of Stephen Harper; led the country’s chief statistician to resign in protest; and cast a spotlight on the broad array of people who depend on the census and care how it is conducted.

TODAY is World Statistics Day—an event you've probably never heard of, but which has special resonance in Canada, where one of the hottest political debates of recent months has involved number-crunching. The question of whether responses to the long form of the census, sent to a representative group every five years, should be voluntary or remain mandatory may seem rather technical. But it has pitted the country's two largest provinces, Ontario and Quebec, against the minority Conservative government of Stephen Harper; led the country's chief statistician to resign in protest; and cast a spotlight on the broad array of people who depend on the census and care how it is conducted.

The clamour over the census began in June, when the government slipped into a list of cabinet decisions the news that recipients of the long-form census questionnaire would no longer be required to complete it. The government undertook no prior consultation before making the change and never formally announced it.

Mr Harper may have chosen to downplay the new policy simply because he didn't expect it to ruffle many feathers. Denmark scrapped its census in 1970, Germany did so in 1987 and Britain will complete its final tally next year. And had he simply done away with the long-form census altogether while keeping the shorter one mandatory, the move might indeed have gone unnoticed.

However, introducing a voluntary census was asking for trouble. The United States once attempted a similar experiment, but abandoned it after determining that data from voluntary surveys are unreliable, since marginalised groups are less likely to fill out the forms. Moreover, in order to keep the sample size constant despite a reduced response rate, the government would have to send out more forms, at an additional cost of C$30m ($29m). Canadians would be paying more money for less accurate information.

As a result, Canada's statistical gurus staged a rebellion. The government's chief statistician resigned in protest. Advocacy groups representing Francophone Canadians living outside the French-speaking province of Quebec launched an unsuccessful lawsuit, arguing that programmes for minorities require reliable census data on employment, education and immigration status. The Inuit have made a similar claim. The governor of the Bank of Canada said it uses census data to set monetary policy, and may have to look elsewhere after responses become voluntary. And ministers from Ontario and Quebec say they will no longer know how the labour market is changing and where to target spending on training and education.

Sound counter-arguments to these claims may exist. But the government isn't making them. Tony Clement, the industry minister, said he had heard of concerns that the mandatory census represented an invasion of privacy. However, the privacy commissioner promptly revealed that her office had received a grand total of three such complaints in the last decade. He then bemoaned the unfairness of threatening to imprison people for not filling out their census form—which did indeed sound rather draconian, until a search of the records determined that no one had ever suffered this fate, although a few people had been fined. The government's critics say the policy is simply an ideologically motivated sop to a small group of hard-line Conservatives who want less government in their lives.

Despite the uproar, Mr Harper is standing firm. The forms for the 2011 census have been printed, and the prime minister insists it will go ahead as planned, despite a parliamentary motion September 29th and a private member's bill introduced the next day asking it to reverse course. The UN website promoting October 20th as World Statistics Day says it is meant to “to help strengthen the awareness and trust of the public in official statistics.” At Statistics Canada, currently without a chief statistician, the words have a hollow ring.