Contact
There is no contact form, because a form here would mean storing your message somewhere and this site deliberately stores nothing. Email works.
Reporting a wrong figure
These are the most useful messages we get. Include the page address and, if you have one, a source for the correct value — corrections that arrive with a source get applied the same day, and because figures are stored once and reused, fixing one corrects every page that quotes it.
Suggesting a page
If you looked something up here and it was missing, that is worth telling us. Gaps people actually hit are better signal than any keyword tool.
Reuse
Quoting a figure with a link back is fine and welcome. The underlying datasets have their own licences, listed on the sources page; where a source requires attribution, that requirement passes to you as well.