How Much Does This Cow Weigh? : Planet Money We wanted to understand an eerie phenomenon that drives everything from the stock market to the price of orange juice. So we asked you to guess the weight of a cow.
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#### How Much Does This Cow Weigh?

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JACOB GOLDSTEIN, HOST:

Hey, just a quick note - today's show originally aired in 2015.

DAVID KESTENBAUM, HOST:

Francis Galton was the kind of person who believed in experts - you know, people who had studied things, people who knew stuff. He figured they knew things that ordinary people just did not. I mean, of course they did, right?

GOLDSTEIN: Obviously.

One day, Galton goes to a country fair. This was about a hundred years ago in England. And there's this contest going on at the fair - guess the weight of the ox. Galton's a scientist and a statistician. And he figures, hey, I can do an experiment here, right? He figures, I'm going to take everyone's guesses, take the average and compare that to the actual weight of the ox.

KESTENBAUM: We heard this story from James Surowiecki. He's an economics journalist.

JAMES SUROWIECKI: So he thought what you were going to end up with was a really flawed guess because in his mind, what you were doing was you were taking guesses of a few smart people, a few mediocre people and then a lot of morons - 'cause he basically thought everyone was dumb. So he figured the group's guess was going to be way, way off the mark.

KESTENBAUM: The contest organizers gave Galton the little slips of paper with everyone's guesses on them. He took them, calculated the average. The average was 1,197 pounds. And the ox?

SUROWIECKI: The ox weighed 1,198 pounds. So that - in other words, the crowd's judgment was, essentially, perfect.

KESTENBAUM: One pound off?

SUROWIECKI: One pound off.

GOLDSTEIN: This is super creepy, right? Like, what's going on here? Is there some kind of, like, collective unconscious magic?

KESTENBAUM: Yeah, it's like a Ouija board or something, right? But the idea that underlies this - it is everywhere. It's the idea of the stock market - you know, thousands of random people buying and selling shares. Like, when you hear that Apple stock went up or the Dow plunged, that's basically people guessing the weight of an ox.

GOLDSTEIN: Yeah, it's everywhere, right? It's the price of oil. It's the price of orange juice. All kinds of things that are really important to the world work exactly this way.

KESTENBAUM: But why should it work? Why should a bunch of random people - a lot of whom have no idea what they're doing - somehow magically produce an answer that makes sense? Does this really work? And if it does, why does it work?

(SOUNDBITE OF ALESSANDRO RIZZO AND ELLIOT GREENWAY IRELAND'S "LA VIE PARIS")

GOLDSTEIN: Hello, and welcome to PLANET MONEY. I'm Jacob Goldstein.

KESTENBAUM: And I'm David Kestenbaum. Today on the show, Mr. Galton, we redo your experiment.

GOLDSTEIN: What's the cow's name?

KIRSTEN KUZMITCH: Penelope.

GOLDSTEIN: Hi, Penelope. Thanks for letting us weigh you. Can I pet her?

KUZMITCH: Yeah.

GOLDSTEIN: She's chewing.

KESTENBAUM: One pound off - come on.

(SOUNDBITE OF ALESSANDRO RIZZO AND ELLIOT GREENWAY IRELAND'S "LA VIE PARIS")

GOLDSTEIN: So we came up with a plan to repeat Galton's experiment. Find a fair and a cow and a big scale to weigh the cow. And then...

KESTENBAUM: In secret. In secret.

GOLDSTEIN: And then we were going to throw the question out to the crowd, ask the world, how much does this cow weigh?

KESTENBAUM: We didn't want to just limit it to people at the fair. So we figured we'd take some pictures, post them online and ask the whole world to guess.

GOLDSTEIN: So we went out to a county fair in Burlington County, N.J. We met Penelope the cow in the dairy tent. She was sitting on a bunch of hay.

KESTENBAUM: Kirsten Kuzmitch (ph) was taking care of her.

GOLDSTEIN: Can you just describe what she looks like?

KUZMITCH: Yeah. She's mostly black. She has white legs, and she has a white spot in the middle of her head. But she's a big black cow (laughter).

KESTENBAUM: What did you just say?

GOLDSTEIN: I said holy cow without even realizing what I was saying. She's much bigger. She just stood up. She's walking out of the barn now. And she's way bigger than I thought when she was sitting down.

KESTENBAUM: We took some pictures of you, Jacob, standing next to the cow for scale. And just for fun, we decided to ask people at the fair how much they thought Penelope weighed. As it happened, it was kids day, so there were a lot of kids around.

UNIDENTIFIED CHILDREN: Hi, Penelope.

GOLDSTEIN: Which was fine. You know, they're nonexperts.

UNIDENTIFIED CHILD #1: Caleb (ph).

KESTENBAUM: How much do you think Penelope weighs?

UNIDENTIFIED CHILD #1: Six pounds.

KESTENBAUM: How'd you come up with that number?

UNIDENTIFIED CHILD #1: 'Cause I'm 6 years old.

GOLDSTEIN: You guys want to guess how much this cow weighs.

KARIN: Yes, sixty-hundred pounds.

GOLDSTEIN: Like 6,000?

KARIN: Yes.

GOLDSTEIN: OK. Do you know how much you weigh?

KARIN: Not at all.

KESTENBAUM: I'm sympathetic. Looking at Penelope, I had no idea how much she weighed. Like, I didn't even know how to think about it. Did she weigh more than my car? Did she weigh less than my car? I don't even know how much my car weighs.

GOLDSTEIN: (Laughter) More than a cow. I'm going to say more than a cow.

We found an older group of kids. And, yeah, they also guessed on the low side. But they had this bigger problem, this, really, more worrying thing. And it was a problem that adults also seemed to have. And it was this. The first kid said a number. And then all the other kids said basically the same number - numbers that were, like, too close to the first kid's.

KESTENBAUM: It's like they were incapable of guessing anything different.

ESA: My name's Esa (ph).

GOLDSTEIN: And, Esa, how old are you?

ESA: I'm 10.

KESTENBAUM: And how much do you think that cow weighs?

ESA: Two-hundred pounds.

GABRIELLA: My name's Gabriella (ph). I'm 10. And I think the cow weighs 300 pounds.

UNIDENTIFIED CHILD #2: My name is Caleb (ph), and I am 7 years old. And I think the cow weighs 300 pounds

KESTENBAUM: Oh, Caleb (laughter).

People are not that different from cows. We heard. If we don't know something, we look for a leader, even if the leader maybe doesn't know anything.

GOLDSTEIN: Penelope finished chewing, and we took her over to be weighed. It's actually pretty unusual to want to weigh a cow. And the scale they had at the fair was not for cows.

What kind of scale is this?

UNIDENTIFIED PERSON: It's actually like - a truck scale is what it's for - same style of scale I'll use for big trucks and stuff, which we use it to weigh the tractors during the tractor pull.

KESTENBAUM: But it'll work for a cow?

UNIDENTIFIED PERSON: Yep.

GOLDSTEIN: Kestenbaum, you were obsessed...

KESTENBAUM: Paranoid.

GOLDSTEIN: ...Arguably paranoid about keeping the results of this secret. You didn't want it to leak out, I guess.

KESTENBAUM: Yeah. And all these people had gathered.

Actually, can we clear - can we seriously clear everybody out except for just a minimum of people? Like...

GOLDSTEIN: Can we swear you to secrecy?

UNIDENTIFIED PERSON: I'll swear.

KESTENBAUM: OK, just you. Everybody else over there.

Kirsten walked Penelope up onto the scale.

KUZMITCH: Easy.

KESTENBAUM: And we watched this little digital display.

KUZMITCH: Whoa.

UNIDENTIFIED PERSON: Yep.

GOLDSTEIN: OK. It's 1,355 pounds.

KUZMITCH: We're good?

KESTENBAUM: One thousand, three hundred and fifty-five pounds. We walked Penelope back to the dairy tent, and then we went home.

GOLDSTEIN: The next day, we posted photos online of...

KESTENBAUM: Of the cow and you.

GOLDSTEIN: And me, right. I was there to give some sense of perspective.

KESTENBAUM: We put you on the tractor scale.

GOLDSTEIN: Yes, 165 pounds. That's how much - that's how much I weigh.

KESTENBAUM: Then our colleague, Quoctrung Bui, here put it all up online. Guess the weight of this cow.

GOLDSTEIN: And the idea was - our hope was that lots and lots of people would guess because the fundamental question here - the thing we're trying to figure out - is, if you have a bunch of random people making their best guess at something, do you get close to, you know, the truth? Do you get close to the right answer? So we put it up, and we waited for the results to come in.

KESTENBAUM: All right. It's been up for how long now?

GOLDSTEIN: Two minutes.

KESTENBAUM: How many entries?

GOLDSTEIN: There's 15 entries.

GOLDSTEIN: OK, here we go.

KESTENBAUM: It's still 15?

GOLDSTEIN: Still 15.

KESTENBAUM: Come on. Oh, my God. That's all we're going to get - 15.

GOLDSTEIN: I'm going to retweet this.

KESTENBAUM: (Laughter) You're worried it's already been buried after two minutes.

GOLDSTEIN: (Laughter) I know.

We also showed the pictures of me and the cow to James Surowiecki. He's the New Yorker writer we talked to at the beginning of the show. He actually wrote a book called "The Wisdom Of Crowds." So we asked him to guess.

KESTENBAUM: Remember here, the actual weight of the cow - 1,355 pounds.

SUROWIECKI: All right. I will guess that the cow weighs 725 pounds.

KESTENBAUM: How did you come up with that number?

SUROWIECKI: I don't know - maybe looks like four- or five-times Jacob's size, I guess. Although I'm sure cows are - well, I don't know. Are they denser or not than humans? So you know, whatever. It's pretty random, actually.

KESTENBAUM: Pretty random and pretty wrong. We told him Penelope's actual weight - twice as heavy as his guess.

SUROWIECKI: (Laughter) It's so bad. It's a sad commentary that someone who's been talking about an ox for this long has absolutely no clue how much a cow weighs.

KESTENBAUM: If we get a crowd of people like you, it's going to be terrible.

SUROWIECKI: We're going to be in bad shape. I'm praying somebody was guessing 2,200 on the other end.

GOLDSTEIN: Because the key question is, what's the average going to be, right? Is the crowd going to get it right? Or at least how close are they going to get? So we left this up online for five days - let people guess for five days. Our colleague, Bui, tallied it all up. David, you and I came into the studio. We didn't know the results. And Bui came in to give us the numbers.

KESTENBAUM: First of all, how many people guessed?

QUOCTRUNG BUI, BYLINE: So the number of people that guessed - 17,205 people.

GOLDSTEIN: Seventeen thousand? That's legit. That's good. That's good.

BUI: It's as if you got, like, a small town to all guess.

KESTENBAUM: Bui took those guesses, added them up and calculated the average. This was the big moment.

BUI: You guys ready? One thousand, two hundred and eighty-seven pounds.

KESTENBAUM: One thousand, two hundred and eighty-seven? Penelope actually weighed 1,355.

GOLDSTEIN: Pretty close, right? So that's to within, like - what? - 60-ish pounds?

KESTENBAUM: That was pretty impressive.

GOLDSTEIN: Yeah. I mean, they're only, like, 5 percent off, you know? And, OK, sure, the Galton thing was 1 pound off. This isn't that. But remember, this is just a bunch of random people, you know, looking at this little cow picture in their Facebook feed on their iPhone.

KESTENBAUM: And here's another amazing thing. When we asked people to guess, we also asked them this other question. We asked, are you an expert? Have you ever worked with cows? Because remember, Galton thought experts might be better. And 3,000-some people answered yes to that question. Jacob, you wondered, were they really, really experts?

GOLDSTEIN: I mean, sure. These are just people clicking a button online. So we emailed a bunch of them, and we heard back. And they did seem pretty expert. You know, a lot of them were farmers. One of them mentioned the, quote, "absence of a visible udder."

KESTENBAUM: Actually, a few of them mentioned that.

GOLDSTEIN: (Laughter) And apparently that tells you something about how old the cow is - how much it weighs.

KESTENBAUM: So how did the experts do? Here's the answer.

BUI: So the average guess for the experts was 1,272 pounds.

KESTENBAUM: They're worse.

BUI: They were worse. It's amazing.

GOLDSTEIN: So OK - so maybe that is wisdom of the crowds.

KESTENBAUM: To be fair, the experts were only marginally worse, but they did not beat the crowd.

GOLDSTEIN: We told Surowiecki about these results, and he wasn't surprised. In fact, he writes in his book, chasing the expert is a mistake. We should ask the crowd.

KESTENBAUM: And the fact that the larger crowd got it to within 5 percent - he said that seems about right to him. When people do versions of this experiment - asking people to guess the number of jelly beans in a jar, for instance - the crowd usually gets it to within 3 to 5 percent.

SUROWIECKI: You know, one of the things that's interesting about this is even though I've written a book and done this experiment a number of times, every time I do it and every time I hear the results, I'm like, it's not going to work this time...

(LAUGHTER)

SUROWIECKI: ...Because the idea is so counterintuitive. You know, it's pretty extraordinary in that regard. The power of this - to actually let the group arrive at really good decisions is - it's eerie. There's something eerie about it, I think.

KESTENBAUM: It is eerie, right?

SUROWIECKI: Yeah, it is. There's something magical about it that seems magical, I think. It's not magic. It's just math, but it seems magical.

KESTENBAUM: Surowiecki says the reason this seems to work is that every person's guess is contributing some new, little piece of information. Everybody is different. Everybody thinks slightly differently when they're trying to guess the cow's weight. Maybe one person studies that photo of the cow from the side. Some people are probably trying to figure out how many Jacobs would fit in the cow. Someone else might know how much a horse weighs and kind of go from there.

Like, every person's guess in some ways reflects their specific life experience of judging the size of things in the world just from decades of living. It's like every person's mind is a different scale for weighing the cow.

GOLDSTEIN: Any one of those scales isn't going to be a great scale, right? Each one of those is probably going to be wrong. There's going to be some error in every single one.

KESTENBAUM: They're good in some way, but they also have some problem with them.

GOLDSTEIN: Yeah, and one of the essential things is those problems tend to cancel each other out, right? Maybe one person is wrong 200 pounds high, but the next guy is wrong 200 pounds low. So the wrong parts - the wrongness - kind of washes out. And in the end, what you're left with is all those little bits of information. And the result is amazingly good. You know, collectively, we do seem to know what we're doing.

KESTENBAUM: Surowiecki says there are certainly times when this does not work, like think stock market panics or bubbles.

GOLDSTEIN: Yeah. A big problem is that thing we saw with the kids at the beginning, where one person says a number and then everybody else around him just kind of latches on to that number. There's actually a technical term for this. It's information cascade.

KESTENBAUM: It's like, my neighbor just bought a house. That seems like a lot of money to pay for a house, but he did fine. I'm going to do the same thing. Or everyone's buying that stock. It must be a good stock. I'm going to buy it.

SUROWIECKI: The stock market is not perfect, but what is amazing about the stock market is that investors individually, even very good investors, are oftentimes irrational. They have tiny bits of information. They're making decisions based on emotion or on, you know, some tip they got. And yet, collectively, we trust them to set the value of all of these companies. It's kind of scary when you think about it.

But the interesting thing is I don't think there's a better way to do it, and there is not a more effective way of doing it either.

KESTENBAUM: This is why it is so hard to beat the stock market. The wisdom of the crowd is pretty good. And the people who seem to beat it - who say, I can beat the stock market - often, they are just plain lucky.

GOLDSTEIN: In our experiment, for example, there were 15 people who got the cow's weight exactly right. They were off by 0 pounds.

KESTENBAUM: We picked one of them at random as our winner. We called him up to tell him the news and to see how he did it.

(SOUNDBITE OF PHONE RINGING)

HARRIS PAHLLICK: Hello.

KESTENBAUM: Is this Harris (ph)?

PAHLLICK: Yeah. How's it going?

KESTENBAUM: Harris Pahllick (ph) is 20 years old. He's a student at Hamilton College, never touched a cow in his life. In fact, could not even remember his guess. We told him he'd guessed 1,355 pounds and that the weight of the cow was also 1,355 pounds.

PAHLLICK: Oh, my God.

KESTENBAUM: You won.

PAHLLICK: That's amazing. Do you want to know how I got to that guess?

KESTENBAUM: Yes.

PAHLLICK: I Googled it. I Googled average weight of female cow, and it said - here. I'll get it. So it pops up in a little box. And it comes from Dairy Moos - dairymoos.com.

GOLDSTEIN: Dairymoos.com says the average weight of a cow is 1,500 pounds, depending on the age and whatever. Harris looked at the picture of Penelope the cow and said, oh, she looks a little bit on the small side. He went with 1,355. It was just a guess.

PAHLLICK: Yeah, completely guessed.

GOLDSTEIN: So we're going to send you the cheapest plastic cow trophy we can find.

KESTENBAUM: We talked with Harris about what we should put on the trophy 'cause it's a bit of a puzzle, right? Like, should it say, I got lucky? He was actually fine with that. He said that made sense.

GOLDSTEIN: I was pushing for mutual fund manager of the year.

KESTENBAUM: Robert (ph) here suggested, someone had to win. In the end, I think we are just going to say congratulations.

(SOUNDBITE OF DAVE BETHELL AND GEOFFREY MICHAEL GEIER'S "HAPPY IS AS HAPPY DOES")

KESTENBAUM: Congratulations.

(SOUNDBITE OF DAVE BETHELL AND GEOFFREY MICHAEL GEIER'S "HAPPY IS AS HAPPY DOES")

KESTENBAUM: All right, we got some footnotes. You know how at the end of research papers they put all the technical details there? A couple things we want to tell you - when we calculated the average of the guesses, we did throw out outliers, like the person who just held down the nine key as their guess - nine, nine, nine, nine, nine.

GOLDSTEIN: Nine, nine, nine, nine, nine, nine, nine, nine, nine.

KESTENBAUM: Thanks for that. Also, for people who love the median, we calculated the median, too.

GOLDSTEIN: I am a median lover. The median is the value in the middle where half the guesses are higher, half the guesses are lower. The median was pretty close to the average. The median was 1,245 pounds - within 8 percent of Penelope's actual weight. The median expert guess was a little worse, but pretty close. You can find all the numbers online at npr.org/money. Also, there are some pictures of Penelope the cow, among other things, on our Instagram feed, @PlanetMoney.

And one other thing - PLANET MONEY has a new weekly email newsletter. It's great. There are all these interesting questions, like, do plastic bag bans help or hurt the environment? Also, why did a bunch of countries in Europe try a wealth tax and then give up on it? You can subscribe to the PLANET MONEY newsletter at npr.org/planetmoneynewsletter.

KESTENBAUM: You can also email us - planetmoney@npr.org. Thank you also to everybody for guessing. Thank you to Penelope the cow and to Rosemary Kay and the other folks at the Burlington County Farm Fair.

GOLDSTEIN: This show was originally produced by Nadia Wilson. Today's rerun was produced by Liza Yeager and Rachel Cohn. Bryant Urstadt edits PLANET MONEY. Alex Goldmark is our supervising producer. I'm Jacob Goldstein.

KESTENBAUM: And I'm David Kestenbaum. Thanks for listening.

How heavy is the cow?

SANDY REO: Absolutely no idea. (Laughter) Absolutely no idea. I really wouldn't...

KESTENBAUM: Like, does 10,000 pounds sound too heavy, or who knows?

REO: I really have no idea.

KESTENBAUM: Twenty-thousand pounds?

REO: Twenty-thousand, I think, is going over the limit - yeah, no.

KESTENBAUM: So less than 20,000.

REO: Less than 20,000.

KESTENBAUM: More than 5 pounds.

REO: More than 5 pounds - more than a bird.