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Mine doesn't have nationality on it - just your first language still spoken, and questions about marital status, which I feel are irrelevant and intrusive.
There are two forms; The short form with basic Qs (sent to 80% of households) and the long form (sent to 20%). The changes in the composition of the latter over time are themselves an interesting reflection of what policy makers consider interesting or important.

Believe it or not, this is one of the few things the feds do that is very usueful. Ridings get redistributed according to the results of the census, transfer payments and social services delivery is decided in part based on census data and the private sector uses it heavily to make marketing and site allocation decisions. That it is quinquennial as opposed to decennial (as is the case in the US) makes it even more useful.