The Plymouth Ox and the Hidden Wisdom of Crowds
An elderly scientist buys 800 used tickets at a livestock fair. What he discovers will challenge centuries of skepticism about the judgment of ordinary people.
Sixpence to guess the weight of an ox
The annual Fat Stock and Poultry Exhibition, Plymouth, autumn 1906. Amid mud trampled by thousands of boots and the sharp smell of manure and wet wool, a large ox stands motionless in its pen. Around it, a small crowd gathers before a booth selling numbered tickets at sixpence each.
The game is simple: write your name, address, and your estimate of the animal's weight once slaughtered and 'dressed' — meaning stripped of head, feet, and innards. Closest guess wins a prize. Butchers with calloused hands, farmers who had weighed livestock all their lives, curious onlookers taking wild guesses. Eight hundred tickets sold in a few days.
None of those present suspected that these slips of paper, once the winners were drawn, would end up in the hands of a man who would use them to answer one of the oldest questions in political philosophy.
The aristocrat who distrusted the masses
Francis Galton was eighty-five years old. Darwin's cousin, inventor of fingerprint identification, pioneer of modern statistics. A man who had spent decades measuring skulls, classifying intelligence, theorizing that genius was hereditary and that important decisions should be left to the best.
Yet something gnawed at him. England was changing. Suffrage was expanding, the masses demanded a voice. Colleagues at the club spoke with horror of the 'tyranny of the majority.' But Galton was first and foremost a scientist: opinions needed verification through data.
"The judgments of the competitors were not distorted by passion, nor influenced by rhetoric," he later noted. The sixpence fee had kept jokers away. The hope of a prize had pushed everyone to try their best. It was, in essence, a miniature model of democracy: ordinary citizens expressing judgment on something they didn't fully understand, guided by partial experience, intuition, information gathered here and there.
787 slips on the workbench
Galton discarded thirteen tickets — illegible or incomplete. 787 remained. He arranged them in ascending order of estimate, converted units to pounds, built tables and diagrams. He sought the median: the value that divides the estimates exactly in half, the one that according to the democratic principle of 'one vote, one value' represents the collective voice.
The ox, slaughtered and weighed, came to 1,198 pounds.
The crowd's median estimate: 1,207 pounds. A difference of nine pounds. 0.8 percent.
Less than one percent
Galton reread the numbers. The crowd — that chaotic mass of competents and incompetents, experts and amateurs — had erred by less than one percent. No single individual could have done as well with certainty. Wisdom resided in no particular brain but emerged from the imperfect sum of imperfect judgments.
"The result speaks more favourably for the trustworthiness of a democratic judgment than might have been expected," he wrote in Nature in March 1907. For a man who had devoted his life to demonstrating the superiority of a select few, it was a remarkable admission.
He also noticed something strange: errors were not symmetric. Those who overestimated tended to err more (45 pounds above the median) than those who underestimated (29 pounds below). He couldn't fully explain it — he hypothesized psychological reasons, perhaps different calculation methods among competitors. He left the question open, as an honest scientist does.
A forgotten experiment, an idea that returns
The Nature article occupied barely two pages. Few read it. Galton died four years later, in 1911, remembered for eugenics more than for that curious study of a Devon ox.
It took nearly a century for someone to rediscover that data. In 2004, journalist James Surowiecki opened his book 'The Wisdom of Crowds' with the Plymouth story. Since then, Galton's experiment has become the theoretical foundation of Wikipedia, prediction markets, crowdsourcing, algorithms that aggregate reviews and opinions.
It all started with an old aristocrat and his prejudices, 787 crumpled slips of paper, and the willingness to let the numbers surprise him.