Study finds fashion trends repeat every 20 years

By Stephen Beech

Fashion really does revolve on a 20-year cycle - and maths can prove it, according to new research.

Industry insiders and beauty magazines have long cited the “20-year-rule” - the idea that clothing trends, from miniskirts to bell-bottoms, often resurface every two decades.

Now American scientists have discovered that observation isn’t just anecdotal, it’s a mathematical reality.

Researchers at Northwestern University in Illinois, developed a new mathematical model - using the most comprehensive fashion database to date - showing that trends tend to cycle roughly every 20 years.

By analyzing around 37,000 images of women’s clothing spanning from 1869 to today, the team found that styles rise in popularity, fall out of favour and then eventually experience renewal.

Along with supporting common perceptions about the life cycles of fads, the researchers say their findings could help explain how new ideas spread in society.

Study lead author Dr. Emma Zajdela said: “To our knowledge, this is the first time that someone developed such an extensive and precise database of fashion measures across more than a century.

“We have some very interesting results, including that the (20-year) cycle we uncovered in the data matches industry knowledge.

"Historically, the lack of data posed a barrier to explicit quantitative study of this system.”

Dr Zajdela, a postdoctoral fellow at Princeton University and a research fellow at the Santa Fe Institute, conducted the work while a doctoral candidate at Northwestern’s McCormick School of Engineering.

She and her colleagues drew from historical sewing patterns from the Commercial Pattern Archive at the University of Rhode Island and runway collections to analyzed tens of thousands of garments dating back to the late 1800s.

The team measured key features of dresses - hemline, neckline and waistline positions - turning clothing designs into numerical data that could be measured and tracked across decades.

To analyse the data, the researchers built a mathematical model based on a simple idea: the tension between wanting to stand out while still fitting in.

Once a style becomes too common, designers move away from it - but not so far that the clothes become unwearable.

Study co-author Dr. Daniel Abrams said: “Over time, this constant push to be different from the recent past causes styles to swing back and forth.

“The system intrinsically wants to oscillate, and we see those cycles in the data.”

The tram found that the results revealed a "striking" pattern: while fashion evolves gradually over time, the rise and fall of styles follows a repeating wave that peaks roughly every two decades.

Dr. Zajdela says one of the clearest patterns involves hemline length.

Over the past century, skirt lengths have repeatedly shortened and lengthened - from shorter flapper dresses in the 1920s to longer, more conservative styles in the 1950s, and then to the miniskirts of the late 1960s.

But that pattern loses its clarity in recent decades.

Starting in the 1980s, the data show a wider range of skirt lengths appearing at the same time, suggesting that fashion trends are becoming more fragmented.

Dr. Zajdela says that rather than one dominant trend, niches emerge, reflecting more diversity in fashion.

She added: “In the past, there were two options — short dresses and long dresses.

“In more recent years, there are more options: really short dresses, floor-length dresses and midi dresses. There is an increase in variance over time and less conformity.”

Dr. Zajdela presented the findings at the American Physical Society (APS) Global Physics Summit in Denver.