An employee makes his way to work at Statistics Canada in Ottawa. Statistics Canada has run the census since 1971; before that, the agency — originally established in 1918 — was called the Dominion Bureau of Statistics. (Sean Kilpatrick/Canadian Press)Governments have had a keen interest in knowing how many people lived within their borders — and what they produced — for a very long time.

Go back almost 6,000 years to Babylon and bureaucrats were counting donkeys, oxen, butter, milk, honey and wool. In ancient Egypt, government workers counted people — mainly to assess the labour force available for building pyramids.

In 1491 BC, in what's now Israel, people were counted to determine who was eligible for military service and who could be taxed.

In 1665, Jean Talon was given the task of counting the inhabitants of New France. The first census on what would later become Canada tallied 3,215 people — excluding First Nations and royal troops.

A return sheet from the 1911 Census of Canada, taken in the St.George Ward of Ottawa, from the Library and Archives Canada. Talon and his staff went door to door to gather the names of inhabitants, as well as information on age, sex, marital status, trade and occupation. They also collected information on livestock and land under cultivation.

The first national "decennial" census — that's a census held at the beginning of a decade — was mandated by law in British North America beginning in 1851. That law required a census be taken in 1851, 1861 and every tenth year after that.

The census of 1871 was the first after Confederation. The questionnaire was available in English and French, as has been in every census since. A total of 3,689,000 people were counted in that census.

In 1905, the census office became a permanent part of the Canadian government. Thirteen years later, the Dominion Bureau of Statistics was established under the Statistics Act.

Censuses were taken every five years in Manitoba, Saskatchewan and Alberta since 1906. In 1956, the federal government moved to a national census every five years to provide a better means of measuring the pace of economic growth and urbanization. But it wasn't until the Statistics Act was passed in 1971 that it became mandatory to conduct a nationwide census every five years. The legislation also changed the name of the Dominion Bureau of Statistics to Statistics Canada.

There was another major change that year: for the first time, people could fill out the questionnaires by themselves and mail them in.

Five years later, the definition of "head of family or household" was changed. Up to 1971, head of household or family had been defined as the husband, the parent where there was only one parent living with unmarried children, or any member of a group sharing a dwelling equally. In 1976, the census redefined "head of household" as the husband or the wife.

In 1981, the "head of household" term was dropped entirely. Relationships between household members were defined on the basis of the person who completed the questionnaire for the rest of the household, known as "Person 1."

Other notable changes to the information collected under the census:

• 1991: Common-law status.
• 1996: Unpaid work and mode of transportation to work.
• 2001: Same-sex couples and language of work.
• 2006: Canadians can complete their census questionnaire over the internet.