OTTAWA - The prime minister's hometown can't make sense of the census switch.

Stephen Harper's Conservative cabinet recently decided to cut the 35-year-old mandatory long census form next year in favour of a voluntary survey.

That's not going over well with those who run the City of Calgary, where Harper's riding is located and in the middle of the bedrock of the Conservative political base.

Calgary, like other municipalities, relies on the very detailed information from the long census to deliver services and plan for items ranging from low-income housing, to transportation and business development.

Information on areas such as education levels, ethnicity, income and employment can be drilled down to the neighbourhood level using the long census data.

Industry Minister Tony Clement has said the decision to eliminate the mandatory long form was based on the fact an unspecified number of Canadians has complained about the coercive and intrusive nature of the process. Those who refused to fill out the form faced prosecution and fines.

"Every MP has had complaints like that so this year we decided to at least try another method that could be a sound method that would beat the issue of concern of degradation of data, and deal with the issue of coercion and too much intrusiveness," Clement told The Canadian Press.

Derek Cook, Calgary's research and social planner, said eliminating the mandatory nature of the census will make it unlikely there will be any useable data on neighbourhoods. The current census is sent out to a carefully selected series of households per community, to ensure as accurate as possible snapshot of the country.

"If we don't have that data at the neighbourhood level, we're crippled," said Cook, who has worked at the city for 11 years.

Cook rejects another argument made by Industry Minister Tony Clement -- that the impact on the data will be mitigated by sending the voluntary surveys out to 33 per cent of households rather than 20 per cent.

He and other economists, statisticians and other planners have said because certain groups of Canadians are unlikely to fill out the form, the numbers will carry a bias it will be difficult to adjust for.

"Low-income households are less likely to fill it out, we know that," said Cook. "How do we assess the need for affordable housing if we have no reliable low-income data to base our affordable housing plans on?"

Cook's counterpart at the city of Red Deer, Alta., has similar concerns.

"Imagine nobody answers that survey from those smaller communities, that means there will be a total blackout of information from those communities," said community researcher Franklin Kutuadu. "How do you plan for communities, when you can't get a source of reliable information?"

Cook said in his 11 years at the city, he had not heard a citizen gripe about the census. He and others who work with the numbers point out that under the old model of one-fifth of households getting the long census, a household would be required to fill one out once every 25 years.

Both Calgary and Red Deer are preparing responses to the federal government's decision. Kutuadu says another big problem with changing the methodology of the long form census is that there will be no way to safely compare numbers from previous years and analyze trends.

"We look at how our population has changed over five years, so in the absence of the long form to collect most of this data, we won't be able to do that," said Kutuadu.