there is a silver badge called census that is linked to a survey.
where can I see this survey?
The annual Developer Survey is announced at stackoverflow.blog. The link to the announcement is usually featured in the yellow box at the top of the right-side sidebar, under the Blog section. Additionally, for the duration of the survey, you should be able to see a ribbon-like banner at the top of every page if not on every SE site then at least on Stack Overflow. If memory serves, the banner both prompts you about the survey and links to the survey page.