STEVE INSKEEP, HOST:
You know, if you actually read the labels on food you eat you'll find some curious things. David Kestenbaum of our Planet Money Team recently found himself staring a pack of M&Ms and he saw one number of particular that seem odd.
DAVID KESTENBAUM, BYLINE: I had gone down to the lobby of our building here to buy a snack and I couldn't decide which kind of M&M to get. So I bought two packs - one regular M&M, one peanut butter filled M&M. In the elevator back up to the office I found myself reading the packaging and I noticed this strange thing. Here I have one - a pack of original M&M weighs 1.69 ounces. The peanut butter ones - slightly less 1.63 ounces. They were the same price, a dollar each, but you get slightly less of the peanut butter M&Ms, 0.06 ounces less - it's a tiny difference way down at the third decimal place. I wanted to know why so I reached out to Mars, the company that makes M&Ms, and while I was waiting to hear back I made some other calls and I discovered this whole weird world.
BILL EDWARDS: You should appreciate, actually, that the confectionery industry is incredibly secretive.
KESTENBAUM: This is Bill Edwards, he used to work for of Mars' big rivals - a company called Rowntrees that makes a British candy called Smarties that are very similar to M&Ms.
EDWARDS: I mean, more secrets have escaped the places where they make nuclear weapons than have ever escape the places from the major confectionery firms.
KESTENBAUM: Edwards spent a lot of time reverse engineering his competitors products and he had a theory here. Maybe, he said, peanut butter M&Ms are more expensive to make so they put fewer in the package. As a way to keep the profit margin the same.
EDWARDS: You're not going to do wonders for your business if you bring out a new product that is less profitable than the existing ones.
KESTENBAUM: Oh, so like if you had M&Ms that were out there - there's a certain profit margin - you're going to introduce peanut butter M&Ms. You would never want to introduce that where you're going to make less money on each pack.
EDWARDS: No, no.
KESTENBAUM: But then having proposed this beautiful theory, he basically rolled it out. peanut butter, he says, is actually less expensive. So if anything, he'd expect you to get more in a peanut butter M&M package. So much for the economic explanation, maybe there was a scientific one. Is it okay if I buy a lot of M&Ms? I went back down to the little store the lobby and I bought what scientists would call a statistically significant sample size. 10 of these 10 of these. I took the M&Ms up to Columbia University to a guy who had a really, really precise scale, Sanat Kumar. He's chair of the Chemical Engineering Department.
SANAT KUMAR: This is a tenth of a gram, and is going to a tenth of a milligram. So a thousand times smaller than what you are looking for.
KESTENBAUM: This a thousand times more accurate than we need?
KUMAR: That right. Talk about a little bit overkill right? (Laughing) So let's zero that.
KESTENBAUM: Sanat had a different theory. Maybe, he said, each bag gets filled by a machine that drops a precise number of M&Ms in each bag. If the peanut butter ones were just a little bit lighter - that could explain why the package came out lighter. So we started counting.
KUMAR: 10 12 14 16 18.
KESTENBAUM: One bag had 28. Another had 26.
KESTENBAUM: Ok, 27 28 - so they are not keeping the number constant.
KUMAR: It's all over the map. This is truly amazing. I have no idea what they're doing.
KESTENBAUM: Another beautiful theory destroyed by data. We did discover something weird though - something that somehow I had never realized what I was eating these things. The peanut butter M&Ms and Ms and the regular M&Ms are like totally different species. The original chocolate M&Ms are these small very precise candies with precise weights. The peanut butter M&Ms, by comparison, are monsters - they're larger, they're lumper and more irregular. As Sanat puts it, the weights had a larger standard deviation. We measured on the fancy scale.
KUMAR: 1.62, 2.0 - fluctuation is amazing.
KESTENBAUM: The larger size turns out to be key to the whole puzzle. I got an email back from the Mars company declining our interview request but including a statement which explained that for health and nutrition reasons all Mars products are designed to be 250 calories or less per person. Calories - we did the math. It turns out because the peanut butter filled ones are so big if you add just one more of them to these little packages you would push the calorie count over 250. That, it seems, is why the package weighs a little less. Nothing to do with the price of peanuts compared to Cocoa - or with the machine that fills the little bags. Calories. I sent a follow-up email asking why the peanut butter M&Ms were so much larger. I got back a one sentence response, quote, "because of proprietary reasons we are unable to elaborate on the size of peanut butter M&Ms". David Kestenbaum, NPR news.
(SOUNDBITE OF SONG, "PEANUT BUTTER JELLY TIME")
INSKEEP: It's MORNING EDITION from NPR News.
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