Tally sticks were made from willow harvested along the banks of the Thames in London. The stick would contain a record of the debt. It might say, for example, “9£ 4s 4p from Fulk Basset for the farm of Wycombe”. Fulk Basset, by the way, might sound like a character from Star Wars but was in fact a Bishop of London in the 13th century. He owed his debt to King Henry III. Now comes the elegant part. The stick would be split in half, down its length from one end to the other. The debtor would retain half, called the “foil”. The creditor would retain the other half, called the “stock”. (Even today British bankers use the word “stocks” to refer to debts of the British government.) Because willow has a natural and distinctive grain, the two halves would match only each other. As Tim Harford explains, the tally stick system enabled something radical to occur. If you had a tally stock showing that Bishop Basset owed you five pounds, then unless you worried that Bishop Basset wasn’t good for the money, the tally stock itself was worth close to five pounds in its own right - like money; a kind of debt, which can be traded freely.

Editors: Richard Knight and Richard Vadon

(Photo: Medieval tally sticks, accounts of the bailiff of Ralph de Manton of the Ufford Church Northampton. Credit: National Archives)

How much might global economic output rise if anyone could work anywhere? Some economists have calculated it would double. By the turn of the 20th century only a handful of countries were still insisting on passports to enter or leave. Today, migrant controls are back in fashion. It can seem like a natural fact of life that the name of the country on our passport determines where you can travel and work – legally, at least.

But it’s a relatively recent historical development – and, from a certain angle, an odd one. Many countries take pride in banning employers from discriminating against characteristics we can’t change: whether we’re male or female, young or old, gay or straight, black or white.

It’s not entirely true that we can’t change our passport: if you’ve got $250,000, for example, you can buy one from St Kitts and Nevis. But mostly our passport depends on the identity of our parents and location of our birth. And nobody chooses those.

Editors: Richard Knight and Richard Vadon

(Photo: Irish and UK passports are on display. Credit: Getty Images)

When the great novelist Charles Dickens arrived in America in 1842, he was hoping to put an end to pirated copies of his work in the US. They circulated there with impunity because the United States granted no copyright protection to non-citizens. Patents and copyright grant a monopoly, and monopolies are bad news. Dickens’s British publishers will have charged as much as they could get away with for copies of Bleak House; cash-strapped literature lovers simply had to go without. But these potential fat profits encourage new ideas. It took Dickens a long time to write Bleak House. If other British publishers could have ripped it off like the Americans, perhaps he wouldn’t have bothered. As Tim Harford explains, intellectual property reflects an economic trade-off – a balancing act. If it’s too generous to the creators then good ideas will take too long to copy, adapt and spread. But if it’s too stingy then maybe we won’t see the good ideas at all.

Producer: Ben Crighton

(Image: Copyright stamp, Credit: Arcady/Shutterstock)

From Spacewar to Pokemon Go, video games – aside from becoming a large industry in their own right – have influenced the modern economy in some surprising ways. Here’s one. In 2016, four economists presented research into a puzzling fact about the US labour market. The economy was growing, unemployment rates were low, and yet a surprisingly large number of able-bodied young men were either working part-time or not working at all. More puzzling still, while most studies of unemployment find that it makes people thoroughly miserable, the happiness of these young men was rising. The researchers concluded that the explanation was simply that this cohort of young men were living at home, sponging off their parents and playing videogames. They were deciding, in the other words, not to join the modern economy in some low-paid job, because being a starship captain at home is far more appealing.

Producer: Ben Crighton

(Photo: Hands holding game pad and playing shooter game on TV screen. Credit: Getty Images)

The Egyptians thought literacy was divine; a benefaction which came from the baboon-faced god Thoth. In fact the earliest known script – “cuneiform” – came from Uruk, a Mesopotamian settlement on the banks of the Euphrates in what is now Iraq. What did it say? As Tim Harford describes, cuneiform wasn’t being used for poetry, or to send messages to far-off lands. It was used to create the world’s first accounts. And the world’s first written contracts, too.

Producer: Ben Crighton

(Image: Close-up of clay tablet, Credit: Kotomiti Okuma/Shutterstock)

Tim Harford tells the surprising story of air conditioning which was invented in 1902 to counter the effects of humidity on the printing process. Over the following decades “aircon” found its way into our homes, cars and offices. But air conditioning is much more than a mere convenience. It is a transformative technology; one that has had a profound influence on where and how we live.

Producer: Ben Crighton

(Image: Air conditioning vent, Credit: Dorason/Shutterstock)

In 1853 Elisha Otis climbed onto a platform which was then hoisted high above a large crowd of onlookers, nervy with anticipation. A man with an axe cut the cable, the crowd gasped, and Otis’s platform shuddered – but it did not plunge. “All safe, gentlemen, all safe!” he boomed. The city landscape was about to be turned on its head by the man who had invented not the elevator, but the elevator brake. As Tim Harford explains, the safety elevator is an astonishingly successful mass transit system which has changed the very shape of our cities.

Producer: Ben Crighton

(Image: Modern Elevator, Credit: iurii/Shutterstock)

The contraceptive pill had profound social consequences. Everyone agrees with that. But – as Tim Harford explains – the pill wasn’t just socially revolutionary. It also sparked an economic revolution, perhaps the most significant of the late twentieth century. A careful statistical study by the Harvard economists Claudia Goldin and Lawrence Katz strongly suggests that the pill played a major role in allowing women to delay marriage, delay motherhood and invest in their own careers. The consequences of that are profound.

Producer: Ben Crighton

(Image: Oral contraceptive pill, Credit: Areeya_ann/Shutterstock)

The way educated women spend their time in the United States and other rich countries has changed radically over the past half a century. Women in the US now spend around 45 minutes per day in total on cooking and cleaning up; that is still much more than men, who spend just 15 minutes a day. But it is a vast shift from the four hours a day which was common in the 1960s. We know all this from time-use surveys conducted around the world. And we know the reasons for the shift. One of the most important of those is a radical change in the way food is prepared. As Tim Harford explains, the TV dinner – and other convenient innovations which emerged over the same period – have made a lasting economic impression.

Producer: Ben Crighton

(Image: TV Dinner, Credit: Shutterstock)

“Superstar” economics – how the gramophone led to a winner-take-all dynamic in the performing industry. Elizabeth Billington was a British soprano in the 18th century. She was so famous, London’s two leading opera houses scrambled desperately to secure her performances. In 1801 she ended up singing at both venues, alternating between the two, and pulling in at least £10,000. A remarkable sum, much noted at the time. But in today’s terms, it’s a mere £687,000, or about a million dollars; one per cent of a similarly famous solo artist’s annual earnings today. What explains the difference? The gramophone. And, as Tim Harford explains, technological innovations have created “superstar” economics in other sectors too.

Producer: Ben Crighton

(Image: Thomas Edison Phonograph, Credit: James Steidl/Shutterstock)