Question about national censuses with information about L2 statistics

[Søren Wichmann]

I would like to collect data on how many of a given language's speakers 
use the language as their second language. Ethnologue has some 
information for 200+ languages, but I need more. I suppose that such 
information would be available for many countries in national censuses, 
but they are difficult to locate for an outsider. So if you are aware of 
such censuses for the countries that you are families with I would be 
very interested in the information, and will post a summary.

Søren Wichmann.