One in five people are financially illiterate, incapable of grasping basic shopping conundrums – such as, is that nine-pack of loo roll better value than two four-packs? In a world of ever more complex financial products, it’s never been a better time for companies to rip people off because, frankly, very large numbers of us are rather dim with numbers.

A fascinating study on financial literacy was issued by the OECD this week, comparing financial literacy around the world, using the same Pisa scoring system that ranks abilities in reading and maths. It was focused on 15-year-olds in 15 countries, so it’s not about adults, but my guess is that most people’s literacy at 50 isn’t much better than at 15. It asked some maths-style questions – comparing the cost of loose tomatoes with boxed ones, and checking an invoice for accuracy – but also explored more modern issues around money, such as identifying if that email from your bank is a scam, and the factors that go into insurance costs for a first moped.

What did we learn? Only 12% of 15-year-olds got the questions right. On average 22% had only the most basic financial literacy (in other words, the tomato question foxed most of them). In many countries (except Italy) girls are better than boys with money. Young people who had gained most of their knowledge about money from friends scored much lower than those who frequently discussed it with their parents (hey teenagers, listen to your parents!).

Read more: We will all pay the price for our financial illiteracy | Money | The Guardian