Do you prefer midiskirts that cover your knees to minis these days? When you wear a slip dress, do you sometimes layer a polo neck underneath it? On a lunchtime browse, do you find yourself drawn to a voluminous sleeve? If you are reading this, then the answer is probably yes. The look of 2017 is notably more demure than that of a decade ago. Hemlines have dipped a crucial few inches, from just above the knee to just below it. A collar up to your chin is the norm. Party dresses have sweeping sleeves, rather than plunging necklines. Or, to put it another way: for the simple reason that you are engaged with fashion, you have become a modest dresser.

When Victoria Beckham launched her fashion house a decade ago, her style had already left the Wag days behind. Cleavage and Daisy Dukes had been replaced by neat knee-length dresses whose necklines exposed only the clavicles. Since then her wardrobe – one of the most photographed and most influential in the world – has evolved further. Her clothes are now loose and fluid, concealing the shape as well as the surface of the body.

Meanwhile at Paris fashion week, the signature Valentino look has exerted a powerful slow-burn influence on fashion in the five years it has defined the house. Long, fluid, with a slender shape that hints at the body but doesn’t cling, it is a romantic silhouette – part Brontë heroine, part Renaissance principessa – that has proved catnip to modern party girls bored of LBDs.

Tunic, knit and trousers, all from a selection by Harry Evans

“I’ve noticed a gradual change in silhouette over the five years I’ve been at Harper’s Bazaar,” says editor-in-chief Justine Picardie. “I see it on the catwalk, and I see it in the office. It’s very often a long-sleeved dress, and there’s a kind of gracefulness to it. This season, there are a lot of below-the-knee and full-length looks in the collections, and that’s filtered down to the high street.”

It is intriguing that this mainstream shift toward modesty has taken place at the same time as fashion explicitly aimed at women who dress modestly for religious or cultural reasons has become big business. The Modist made a splash in e-commerce when it launched on International Women’s Day this year with luxury fashion curated for women who cover up. Dolce & Gabbana now sells abayas. Nike stocks hijabs for athletes. At almost every global fashion week, the dominant fashion aesthetic has tilted toward longer hemlines, higher necklines and more voluminous fabric. Cool and covered – concepts that have tended to live at opposite ends of the style spectrum – are converging.

Is there a connection between modest dressing as a cultural and political issue, and modesty as a trend? At a time of heightened tensions around how a multicultural society can live in harmony, fashion is experimenting with the aesthetic of covered woman, which has itself become a kind of visual shorthand for Islam. “I think there is a link,” says Reina Lewis, professor of cultural studies at the London College of Fashion, who has written widely about modesty and fashion. “I’m seeing longer sleeves and hemlines, higher necklines, and more fabric. Not just more cover, but more volume, so it obscures the body’s shape.”

Shirt, £400, and skirt, £740, by Y’s . Socks from a selection by Harry Evans

Fashion reflects the world around it, and women who dress modestly are highly visible both on the streets of modern cities and in media imagery. What’s more, the economics of the fashion industry put covered-up clothes front of mind. Valentino is owned by Mayhoola for Investments, the emir of Qatar’s investment fund. Middle Eastern clients are a significant market for many brands showing in Paris or Milan. Alexandra Shulman, now a columnist at the Business of Fashion after 25 years as editor of Vogue, has observed a shift in the styling of catwalk fashion. Short dresses might be worn over trousers, for instance, rather than alone. “In a Chanel show, say, a good deal of the looks will have been styled in a way that fits modest dressing,” she says. While there is nothing to stop a client buying the short dress without the trousers worn beneath, “the subliminal effect is to make a covered look feel current”.

Ian Griffiths, creative director of Max Mara, saw the casting of hijab-wearing Halima Aden in his latest show as keeping in step with the times. “If you walk down a top-end shopping street in any major city, you wouldn’t be surprised to see a Max Mara coat worn with a hijab,” he told Vogue. “So why shouldn’t our runway reflect that, too?”

So is the modest mainstream a meaningful trend, or a red herring thrown up by the cyclical nature of fashion? “Bodycon has been the norm for so long that covering up has a certain novelty value for young women,” Shulman points out. And while fashion can function as social commentary, it can also be a kind of Rorschach test: we see what is already in our head, as much as what is in front of us. “When the fashion crowd dressed in great swathes of Comme des Garçons back in the 80s, people talked of black crows, not about being modest,” Lewis says. “Covering up has become politicised.”

Shirt, £560, trousers, £460, and shoes, price on application, all be Acne Studios . Skirt from a selection by Nehera

Long dresses mean different things at different times. Erdem took his inspiration for a recent collection of tiered lace floor-length gowns from 1930s Deauville bathing beauties and the shipwrecked wardrobe of a 17th-century lady-in-waiting, Jean Kerr.

Whatever its origins, mainstream modesty is sticking around. Natalie Kingham, buying director of matchesfashion.com, tips a below-the-knee shirt dress as a key look for autumn, and for winter a pleated silk midiskirt with a knit and knee-high boots. Coco Chan, head of womenswear at online retailer stylebop.com, is confident that the polo neck as a layering piece has legs for another year. “With Raf putting it in his first show for Calvin,” she says, “that puts the polo neck right in the frame.”

If any fashion week trend can rival the midi for fashion-week staying power, it is “female empowerment” as a buzz-phrase of post-show designer chat, and many designers have drawn links between the two. Victoria Beckham said recently that a looser silhouette “puts power back into the hands of the wearer rather than the observer”. Where once the miniskirt was championed as a feminist statement because of its message of liberation, now a longer hemline is seen as the badge of a woman who does not feel the need to make her body shape central to her identity.

“I don’t think not being allowed to show their bodies comes into it, for our customers,” muses designer Justin Thornton of Preen, a label that has shifted over a decade from being famous for bandage-tight party frocks to being known for demure, calf-length dresses. “Thea [Bregazzi, Thornton’s wife and co-designer] and I are inspired by our friends, women in the industry, women who work. A more fluid way of dressing is definitely a positive choice for them.”

Shulman recognises this sentiment: “I’m normally the first into a sleeveless dress in hot weather, but two years ago I was in India, totally covered up, and I realised how comforting it was. I felt secure. So it’s true that there can be liberation in it.”

The issue of individual choice lurks in any discussion of female empowerment and modest dressing. Clothes can express what society values in women – and what it fears. These judgments exist everywhere, whether explicitly defined or not. “Dressing modestly can be about a patriarchal community wishing to control women’s sexuality,” Lewis says. “But that’s not specific to any one culture. The reality is women are more judged and regulated than men. Look at the fat-shaming that happens within our secular society.”

Fashion, as ever, is reflecting the world around it, for better or for worse. Onwards and upwards? With hemlines, it’s a little more complicated than that.

Photography: Sofie Middernacht and Maarten Alexander. Styling: Priscilla Kwateng. Hair: Federico Ghezzi using Bumble and bumble. Makeup: Kristina Ralph Andrews using Nars, both at St Luke’s Artists. Photographer’s assistant: Willy Cuylits. Stylist’s assistant: Karolina Kulicka

This article appears in the autumn/winter 2017 edition of The Fashion, the Guardian and the Observer’s biannual fashion supplement