In a recent speech to the UN, US president Donald Trump set out some remarkable figures on the proportion of inmates in European prisons who were foreign nationals.

Citing statistics from the Council of Europe, he references Greece, Germany and Austria, as having rates around 50%.

“In Switzerland, beautiful Switzerland,” he said “72% of the people in prisons are from outside of Switzerland.” These numbers are correct, but why are the percentages so high – particularly in Switzerland?

Tim Harford speaks to Professor Marcelo Aebi, a criminologist from the University of Lausanne, who wrote the prisons report for the Council of Europe.

If you’ve seen a number in the news you think we should take a look at, let us know: moreorless@bbc.co.uk

Presenter: Tim Harford Producer: Tom Colls Sound mix: Rod Farquhar Editor: Richard Vadon