The Guardian reports on a multi-national survey by the Ipsos Mori market research company, comparing people's perception of a number of national statistics with the actual statistics. There's also an interactive quiz which allows you to feel superior to your countrymen. Some of the findings:
(Score: 0) by Anonymous Coward on Thursday December 03 2015, @05:49PM
From the Guardian article, go to the link in the final paragraph, ipsos-mori.com->Interact with the data -> Average age...
How old do you think the average person in [country] is?
And the options are represented in the graph as percentages.
"Yes officer, I am 18% old".