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The Last Show with David Cooper

The Math Behind Fashion's Cycles

24 Mar 2026

Transcription

Chapter 1: What is the significance of fashion cycles in the clothing industry?

3.288 - 14.935 David Cooper

Your above average intelligence brought you here. It deserves above average absurdity. This is The Last Show with David Cooper.

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20.213 - 43.388 Emma Zajdela

cyclical. Should you hang on to that old zoot suit in your closet because it might come back in style? Well, according to the math, yes, it is cyclical. Turns out trends don't just repeat. They sort of oscillate like a little pendulum. Let's jump in with someone who's researched this. She is a mathematician at Princeton. Her name is Emma Jaidela. Emma, welcome to the show. So great to be here.

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43.408 - 59.475 Emma Zajdela

I am glad that the awkward, ugly and unfashionable pieces in my wardrobe might be coming back. This is big news. My girlfriend tells me to throw out my clothes. I guess I don't have to now. You just have to hold on to them for 20 years and then they'll be back. Is that the period? Is that the general rule?

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Chapter 2: How does Emma Zajdela explain the 20-year fashion cycle?

59.495 - 80.323 Emma Zajdela

20 years? That is, we found in the data that we analyzed that the period is 20 years. And what was really exciting to us about this is apparently this has been known in the fashion industry for some time, but it's never been proven. And then when we found it, we were mathematicians. We looked at the data. We found this 20-year cycle.

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80.343 - 100.052 Emma Zajdela

And six months after that, we realized that people had known this in the fashion industry for a long time. I guess it makes sense. Like I look at Gen Z, I'm a millennial. And in the early 2000s, us millennials, when we were young and cool, we kind of like rejected Gen X clothing, you know, like with our skinny jeans and stuff. And now Gen Z, they seem to dress like Gen X, it looks like.

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100.336 - 121.259 Emma Zajdela

Yeah, totally. Although I've also heard that the early 2000s are back right now. So the low-waste genes have been coming back, for example, which would be about 20 years. Some people think that this 20-year cycle might be a generational gap. So exactly what you're saying, maybe your parents are uncool or the generation right before you is not cool.

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121.599 - 139.44 Emma Zajdela

But if it gets old enough and it becomes vintage... And then it becomes cool again. Let's get into the math, though, because you aren't just like some fashion commentator. You actually modeled the math, figured it out. How do you prove something like that? Like you analyze garments. What exactly do you do? Well, that's a really good question.

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139.52 - 158.325 Emma Zajdela

When we first set out to do this, we started to think, okay, how do we even quantify fashion? What does that even mean? And we're mathematicians, so we like to simple things, make things as simple as possible. We originally thought of something along one dimension. So we thought of the width of men's ties that, okay, this would be a perfect thing.

158.345 - 180.473 Emma Zajdela

We could just quantify how big and small the men's ties get over time. Unfortunately, we couldn't find data that would be pretty good on the width of men's ties. So instead, we decided to look at women's dresses. And we collected this amazing database of 100 years of women's dresses. There's around 35,000 dresses that we analyzed.

181.113 - 203.344 Emma Zajdela

And we analyzed them along what I like to call the vertical axis from the head to the feet. So neckline, waistline, and hemline. And part of the reason for choosing Hemline in specific is that there's been this idea for about 100 years or so now that Hemline is inversely related to the economy. I don't know if you've ever heard of this. No, that's a wild connection, but please keep going.

203.645 - 207.57 Emma Zajdela

Yeah, so apparently in the 1920s, some economists came up with this idea.

Chapter 3: What data did Emma use to analyze fashion trends?

207.59 - 225.213 Emma Zajdela

And it had to do back then with the fact that women were silk stockings. And when they had enough money to buy real silk stockings, then the dresses would become short so that they could show them off. And when they didn't, then the dresses would become longer to cover the fact that they weren't real silk stockings. Interesting.

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225.394 - 244.163 Emma Zajdela

OK, so but the hemlines, the necklines, the waistlines, the whatever lines, you really did notice this kind of oscillating 20 year trend. How far does it go back? We did. So it was pretty crazy, actually, when we first looked at this data. It starts from around the 1920s and then goes till today.

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244.224 - 260.99 Emma Zajdela

We have some amount, about 25,000 of our dresses that are for something called the Commercial Pattern Archive. And these are archives of sewing patterns that actually anyone could go online. And I know costume designers do this, for example. It's hosted at the University of Rhode Island.

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261.05 - 284.925 Emma Zajdela

And you could go and you could download images of these dresses dating back to, I think the latest one in the collection is actually in the 1860s. Wow. Although those were all floor-length dresses. So what we found in the data is these really cool two different clusters, I would say. The first one is that there's always floor-length dresses. So the maxi dress is always in, always has been.

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285.726 - 307.292 Emma Zajdela

In the past, it's actually kind of funny, in the 1860s, for example, they would have these long trains, so in some ways would even extend past the length of the floor, if you think of it that way. But so there's this maxi cluster that always exists. And then there's an upper cluster of shorter dresses that oscillates. So this looks like the sine wave that you might have seen in school.

307.332 - 329.451 Emma Zajdela

This just goes up and down over time. But then something happens in the mid-1980s. In the mid-1980s, you have this oscillation, and then this actually starts to split. So instead of having two clusters where you had sort of short skirts that would oscillate and then floor-length skirts, now you have three clusters. You have many skirts.

329.431 - 345.371 Emma Zajdela

midi or these kind of ankle length skirts and then floor length skirts. If fashion does kind of oscillate like that, what could be the reason for it? Is that we're looking for like novelty, something different, but also something a little bit familiar as well? Yeah, that's exactly our idea.

345.491 - 371.214 Emma Zajdela

So the model that we developed to explain these cycles is based on an idea from psychology called optimal distinctiveness. And the idea of optimal distinctiveness is that for innovations to be successful, they need to be different from others, but not too different. There's actually evidence of this in a variety of different human societal aspects. So in music, for example, we've found this.

371.835 - 389.543 Emma Zajdela

We've also found this in art and in literature, that the ones that are successful are these innovations that are different, but not too different. So our idea for the model is based off of this optimal distinctiveness. And we find that you need to be optimally distinct from three factors.

Chapter 4: What mathematical methods are applied to understand fashion trends?

389.523 - 412.73 Emma Zajdela

So you need to be different from the past, but not too different. There's this quote by this French stylist that I really like, Agnes B, that says, the problem with fashion is that it goes out of fashion. So intrinsically, fashion always needs to be different from the past. Then you have kind of a social aspect where you want to be different from others around you, but again, not too different.

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413.271 - 430.117 Emma Zajdela

If you're a little bit different, then maybe you're cool. If you're too different, then you just go into the weird zone. Yeah, you're like an outcast, pariah, iconoclast. And it's true for technology too. I'm thinking like touchscreen phones. Like Apple did not invent the touchscreen phone.

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430.398 - 446.525 Emma Zajdela

There was other products like that on the market, but they just like, I don't know, launched it with such gusto and made it so usable that people think they invented that. But the truth is it wasn't that different from products that were available at the time. Totally, totally. I think it's also exactly about the time at which an innovation comes in.

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446.966 - 464.968 Emma Zajdela

And we have found this in technology and in science that this idea of optimal distinctiveness is true as well. So the technologies that are successful are sort of different, but not too different from others. So fashion does really run on these mathematical cycles to the designers that think they are like once in a generation unique thinkers.

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465.569 - 483.828 Emma Zajdela

I mean, they can be creative, but they probably aren't like, they probably aren't, I guess. Well, I will say that our research is focused on these three axes of neckline, waistline, and hemline. And of course, there's so many different dimensions to fashion that you can mix and match. So there's the shape of the garments, the colors, the patterns.

483.888 - 505.688 Emma Zajdela

I don't know if you've seen that leopard print has been back a lot recently. I know, I know. Much to my dismay. But I guess a takeaway, I mean, yes, you only study dresses. We can't say definitively it applies to suits or blue jeans or stuff. But a takeaway might be if the stuff in your closet is deeply out of style, just wait 20 years maybe. Absolutely.

505.929 - 519.092 Emma Zajdela

Or if it's a little bit out of style, maybe pair it with something that is in style and then you become this optimal distinctiveness and you just become cool again. Are there any other places where the pattern broke where fashion is not cyclical?

Chapter 5: How do societal changes influence fashion cycles?

520.068 - 542.092 Emma Zajdela

Well, I will say, as I mentioned, from the mid-1980s, we start getting a lot more diversity of styles. That's true for hemlines, and that was true for the necklines and waistlines as well. We think that this is because there's less conformity in society overall, or you could think of it also as just more acceptance of diversity. So women in particular are wearing different kinds of styles.

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542.132 - 561.655 Emma Zajdela

That's become acceptable. There's just also so much more information now through social media, for example. There's a big acceleration of trends. So you need to, there's just many more trends that are coexisting at the same time. All right. Well, I'm about to put on my Von Dutch hat and head to the commercial break here. I'm here with Emma Jaidela, a mathematician at Princeton.

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561.775 - 566.14 Emma Zajdela

Emma, I've enjoyed the chat. Thanks for sharing your research with me. Yeah, thanks so much for having me.

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579.383 - 600.588 Unknown

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