A “Dear Economist” correspondent once asked me why people post clips of classic comedies on YouTube, or go to the trouble of writing online reviews, given that there seems to be nothing in it for them. A textbook economics model would say that people would not, in fact, post online reviews or contribute to YouTube. And my answer, in brief, was that they don’t. Far more people read books than write reviews of them, and far more watch YouTube videos than post them. As a broad defence of rational economic man, my answer wasn’t too bad; but as a way of understanding online volunteering, it was useless.
Economic theory is not entirely helpful, either. “Public good provision” is the economists’ name for installing a solar hot water system for the sake of the planet, or endowing a library, or contributing a paragraph to Wikipedia. The trouble is not that economics has no explanation for such contributions, but that it has too many. Perhaps people are pure altruists, motivated by the joy of others. Perhaps they enjoy the process of contributing, whether or not it actually produces something of value. Or perhaps they enjoy the good reputation that comes with being acknowledged as a Doer of Good Deeds.
Until now, most of our understanding of the question has come from laboratory experiments. Given the importance of social context, these experiments may well be giving precise answers to the wrong question.
But a new study by two economists, Xiaoquan Zhang and Feng Zhu, has cast light on this problem. Zhang and Zhu look at the Chinese version of Wikipedia. Wikipedia keeps track of all the changes every registered user has ever made to the site, when the edits were made, and what they were. It also hosts user pages, where individual users can talk to each other and discuss the changes they’ve been making.
The Chinese government has a habit of blocking access to Wikipedia. Zhang and Zhu study a particular episode in October 2005 during which contributors who lived on the Chinese mainland couldn’t reach the site, but contributors from outside could.
The researchers painstakingly isolated 1,707 contributors who had access to Wikipedia during the block. In most cases, the evidence for this was that those contributors had made at least one change to the site while mainland users couldn’t get to it. They found that while the block was in force, contributions from these unblocked users plummeted by more than 40 per cent.
This finding contrasts with some economic models of public good provision, which say that the larger the group, the larger the free rider problem, because any individual contribution will be spread across a large number of people. (An imprecise analogy: you might bring expensive wine to a dinner party because at least you’ll get a glass. You wouldn’t bring it to a house party, where you’re unlikely to get a sip.)
Chinese Wikipedia contributors, on the other hand, got coy when nobody was watching. When a large number of potential readers were cut off from the site, many writers who could have continued to contribute stopped bothering. The most sociable editors – those with active user pages – were the ones most likely to be discouraged.
So now I have a slightly better answer for my Dear Economist correspondent: people are posting those videos on YouTube because they’d really like you to watch them.
Tim Harford’s latest book is ‘Dear Undercover Economist’ (Little, Brown).
What’s your view? To comment on this column please e-mail the FT Weekend Magazine at email@example.com