A dozen pairs of skinny trousers and jeans breathe easily next to a handful of tailored blazers in a compact closet tucked in Aubrie Costello's tiny bedroom.

About 20 shirts - a few graphic T-shirts, crisp button-downs, and Costello's signature cropped tops - also are part of the mix. Lining the windowsill overlooking a narrow part of South Sixth Street are pretty vintage mugs where Costello keeps the jewelry she wears every day.

Even her collection of statement shoes - she fancies color-blocked oxfords and stacked heels - is modest and orderly. This speaks volumes because Costello, who has worked at Bus Stop Boutique for nearly eight years, has a weakness for funky footwear.

"I was destined to be a hoarder," said Costello, known in the local arts community for her 3D paintings on silken textiles. "But when I started getting into self-care, I just didn't want, or need, as much. Every day, I wake up to a clean space. And I love it."

Costello, 30, is among the growing number of people who have been inspired by The Life-Changing Magic of Tidying Up - which has reached near-cult status - to take on a total wardrobe pare-down.

The purge principles outlined in Marie Kondo's New York Times best seller tell us to hold on to only the "stuff" that sparks real joy in our hearts - everything from books to kitchen appliances to your earring collection.

This mantra is particularly effective when it comes to managing our wardrobes because most of us, me included, tend to hold on to clothing out of obligation and fear of the future.

But Kondo, 31, a Japanese organizational consultant, instructs us: Let everything go you don't love in your life. That means it's OK to throw away the sea of red sweaters you received over the years from well-meaning aunts. They've already served their purpose, so thank them and chuck them. The result will be a pristine space that emits a calm and peaceful energy curated to reflect your authentic personality.

"I used to have so many soccer shirts, but I don't anymore," said Jonathan Rostran, a 20-year-old rising Drexel University senior and math major. Rostran embarked on his decluttering mission a year ago after he struggled to change apartments between semesters.

His wardrobe now consists of two pairs of pants, two pairs of shorts, three jackets, and a handful of sweaters and T-shirts. It takes him 15 minutes to get ready in the morning, and now he acquires shirts for only the teams he truly loves.

This Kondo Effect, as defined by retail-trend forecasters, has resulted in an uptick in Salvation Army donations nationwide. And a digital, secondhand market that includes community consignment apps also has emerged, according to Carys Williams, the London editor of global retail forecaster WGSN.

The reasons are varied: Millennials who have graduated with tens of thousands of dollars in debt are living with roommates in apartments much smaller than the sprawling suburban houses in which they grew up.

The slow-fashion movement, currently picking up steam, champions investing in quality pieces, which often create a smaller carbon footprint than fast-fashion's high-quantity pieces, Williams said. So people are slowly spending more, but buying less.

"I find myself just wearing a uniform now," said Skai Blue Media CEO Rakia Reynolds, who cut back on her myriad of bold looks. "There are certain pieces by Balenciaga, AcneStudios, A.L.C. that I wear three times a week. . . . I just don't shop as much."

In past years, the seasonal clean-out made way for new clothes. But Kondo's advice leaves people more time for doing things that don't involve upgrading their wardrobes.

People are "moving toward the immaterial," Williams said, "with mounting evidence suggesting materialism is making us miserable, and a growing desire to be mentally and mindfully fulfilled. This movement, I feel, has some serious legs."

For the last few months, Lauren Altman, 22, has been eliminating pieces that don't fit into her personal style, like floral pants and cardigans. Then in March, she immersed herself in a full-on purge - including books and CDs.

"I thought, 'Why wait? Why am I holding on to these things?' " said Altman, who will start an MBA program in music production in the fall. (She also read Kondo's latest book, Spark Joy: An Illustrated Master Class on the Art of Organizing and Tidying Up.)

There can be, of course, hazards to eliminating everything that doesn't offer up some joy: "Right now, I'm struggling because I'm down to just two pairs of pants." But Altman says it feels good to see her closet filled only with things she likes.

Nicole Miller franchise owner Mary K. Dougherty started to whittle down her wardrobe five years ago, when she turned 50.

But after listening to The Life-Changing Magic of Tidying Up on CD, she was able to let go of things in a way she wasn't able to previously. Adios, crazy prints. Sayonara, uncomfortable platform heels.

"You reach a certain point in your life where clutter becomes a crutch," said Dougherty. "You get stale or stagnant. When you don't let go of what you need, you just get buried in it. I know. I'm in fashion."