I have worked with census materials for more than six years. I have worked with every Canadain Census from 1891-1951. The latter years are still classified, so I have to have security clearance to look at them. That is because the Canadian Census has a 92 year release date, which means that only the years up to 1911 have been released to the public so far.
It may seem weird to think that we have such a long release date, but people lobbied to get such a short one, it used to be 100 years.
The long release date is so that people directly affected by secrets about their families held in the census are dead before their secrets are revealed.
But some of the other documents that people use for geneology do not have such long release dates, may in fact be available at any time, like birth, death and marriage certificates, and the secrets come out anyway.
I used to think that there wasn't really any secret held by the census that could be so bad, until my father started researching his family's geneology.
We discovered that my great-grandfather had been married twice. We haven't yet found any evidence that he was divorced from my great-grandmother before he married again though.
1901 Census has the whole family living on the farm out in the country.
1911 Census, the mother and a few of the younger children, including my grandfather, were living in town by themselves, with the mother working as a laundress to earn money for the family.
1912 Marriage Certificate has the father going by his middle name, but listing the right birthplace and dates and parent's names, marrying a different woman in a Northern mining town.
1914 Death certificate, the father has died in the Northern town. (My mother says "Second marriage was too much for him!")
Now, this information interests my father and I, because we didn't know much about that side of the family. It is actually kind of neat to find out that something so out of the ordinary happened in our family!
But if my grandfather were still alive he might feel very differently about these revelations. If he hadn't known about it, he might not like to discover that his father had abandoned them when he was six years old, only to get married again a few years later. If he had known about it, he might not like that his grandchildren knew about such a shameful part of our family's past.
I never really appreciated the necessity of the 92 year release date until it hit so close to home.