Next year, however, the government is taking a new approach, where fewer details will have to be disclosed. Industry Minister Tony Clement said the decision was taken in response to complaints that the census was an intrusion into privacy.

"The government does not believe it is appropriate to force Canadians to divulge detailed personal information under threat of prosecution," Clement said in a press release.

Without the religious affiliation data the Toronto Catholic District School Board will be left with "a very black hole" in its attempts to keep track of families eligible to send their children to Catholic schools, said Sandra Vitale, the TCDSB's official in charge of voter registration.

She worries it's renters, many of them recent immigrants whose first language is not English, who are least likely to voluntarily fill in a form.

"It's the people who move from one building to another, from one apartment to another," said Vitale. "These are the ones we don't have information on. If they are not obligated to complete a form then they're going to be lost."

There's money on the line for Catholic boards if they no longer have reliable census data on religious affiliation or linguistic communities, said Carol Devine, Ontario Catholic School Trustees' Association director of legislative and political affairs.

"There certainly are grants within the (provincial) funding formula in which the funding for those grants is based on some of the data which will come from the long form of the census," she said.

The Ministry of Education told The Catholic Register there are five different grants or allocations in the school board funding formula which rely on census data. These affect funding for at-risk students from low-income neighbourhoods, immigrant students struggling with English, French schools and programs for native pupils living off-reserve.

The French Catholic school boards will be hit by a double whammy if reliable census data on both language and religion is left to a less reliable survey, said Association Franco-Ontarienne des Conseils Scolaires executive director Carole Drouin.

"To realize our mandate with the Catholic community, to be able to discern where they are and what religious affiliations are present, that's the kind of data we look into," she said.

With more and more French students coming from immigrant families, Drouin worries that a voluntary survey is least likely to capture lower income, immigrant renters whose first language is not English.

Bad data equals bad decision making, said Drouin.

"We're a knowledge-based society. So everybody who is involved in decision making — investors, people who do marketing, people in education, the policy makers — all make their decisions based on data," she said.

Under reporting of low-income households is also a problem for the social welfare agencies Catholic Charities of the Archdiocese of Toronto funds, said executive director Michael Fullan.

"Without that information, they'd be just sky-bluing it," said Fullan.

The archdiocese of Toronto relies on census data in planning parishes and pastoral services, said David Finnegan, the archdiocese's executive director of Planning, Properties and Housing. It contracts Statistics Canada to generate stats from the census specifically for the geographical area.

"We use that to know what the population is within the diocese, what the ethnic breakdown is, what the percentage of Catholics is, what the average household (number) is, etc.," Finnegan said.

The archdiocese relies on Statistics Canada data "to see how can we best be pastorally available to people," said research director Suzanne Scorsone.

"Where do you send the pastors who speak Mandarin or Spanish or Polish? Where are the growing populations? And how do we plan for the future?" she asked. "Up to this point, Statistics Canada has been a treasure trove of exceedingly useful data for the pastoral and also the social service and educational service of the people that our religious body approaches or has cared for in any way at all."