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Tim Harford inspects budget airline Ryanair’s claim that more than 90% of its flights land on time. It is a boast it makes each time its planes land on time, but can More or Less find the numbers to prove it? Meanwhile, the programme hears that schedule padding – the practice of lengthening official journey times to improve punctuality records – is common practice among many international airlines.

Earlier in the series, we brought you the story of a highly influential economics paper - written by two Harvard professors - which had helped shape the debate on austerity in America and Europe, and the graduate student who spotted some problems with it. The issues Thomas Herndon and his professors found with Growth in a Time of Debt, the paper by Carmen Reinhart and Ken Rogoff, have become a cause celebre. But there are those who are warning that this paper is by no means the only one out there which has mistakes in it – millions of others may have too.