What the National Household Survey can’t tell us

More questions about data reliability
An employee make his way to work at Statistics Canada in Ottawa on July 21, 2010. The Canadian Centre for Policy Alternatives says public service spending cuts have mostly focused on service delivery, contradicting the Harper government’s assurances that cuts would spare front-line resources. Statistics Canada will take the largest proportional loss, losing a third of its staff according to the study. THE CANADIAN PRESS/Sean Kilpatrick

Erica Alini explains the limitations of new data from Statistics Canada.

If you care about accuracy, though, you might wish to avoid drawing conclusions about what today’s NHS numbers tells us about income and housing trends. How much has income inequality widened — or shrunk? Are the poor struggling more or less? And what percentage of Canadians used to spend a third or more of their income on shelter five years ago? If you don’t have a Ph.D. in statistics or economics, StatsCan’s friendly advice is: Don’t try to answer those questions on your own. Simple math is enough if you want to use NHS data to, say, see the distribution of low-income people across provinces or ethnic and age groups. But extrapolating trends across the years now requires field-specific expertise. And even the pros must tread carefully, judging from StatsCan’s lengthy guide to the pitfalls of comparing the NHS, a voluntary survey, to the old, mandatory long-form census.

But hey, at least no one was subject to the mostly facetious threat of jail time.

Andrew JacksonArmine Yalnizyan and Toby Sanger add their concerns.

See previously: The Clement caveat