The global used-clothes market is worth $40 billion annually

The global used-clothes market is worth $40 billion per year, according to Boston Consulting Group, and is growing at more than 15% per year. Like all other retail, it's moving increasingly online.

Driving the news: Etsy announced this week that it was buying U.K.-based Depop, a fashion reseller beloved by #teens, for $1.6 billion.

Etsy itself, now boasting a market valuation of more than $20 billion, has no shortage of secondhand clothing, although its audience skews older.

• American fashion resellers Poshmark, ThredUp, and RealReal have all now gone public; European rivals Vinted and Vestiaire have both recently raised money at unicorn-level valuations.

Be smart: All of these platforms have benefited to some extent from speculative activity — people buying items in the hope that they will be able to resell them at a higher price. Another unicorn, StockX, specializes in such trades.

• Depop, however, is mostly an app for the discovery and purchase of items that don't look like they were found at a chain store in the local shopping mall. It's less about collectible handbags, and more about enabling self-expression.
• Used clothes, and items hand-made by influencers, are also much more socially and environmentally responsible than fast fashion.