Secondhand is white-hot right now. 

Between unicorn valuations and IPO plans, some of Silicon Valley's next big things are focused on what was once big, and now back. 

Backers including Goldman Sachs investment arm and Irving Investors were the latest to pump cash into Thredup ($THREDUP), the California-based secondhand clothing site and app that is now making expansions to the brick-and-mortar rack. However, alternative data isn't signaling the startup is continuing to grow - and other secondhand startups are showing data growth beginning to stall. Maybe this is the top. 

Our first chart tracks the last six months' worth of job postings for both Poshmark ($POSHMARK), in green, and Thredup (blue line)- and both have been trending down since early March. The Wall Street Journal reported during this time Poshmark could IPO - but, the company's data isn't suggesting much in the way of growth. The same goes for Thredup, in fact - although having a big funding round from its new investors certainly helps the company buy more time. Also helpful for Thredup is the fact that it's partnering with major retailers, eager to cash in on the brand's reputation for being the world's largest secondhand clothing marketplace. 

There is good news, however - Thredup app downloads appear to be continuing to grow at a steady pace, even if hiring is not. The company's Google ($NASDAQ:GOOG) Play App Store Ratings Count - that is, how many people report back to their phones with a rating of Thredup - continues to grow, and at a steady pace. And, because we can also track app rating, we can tell that most of the company's customers are satisfied customers: Thredup's rating is around 4.5 right now (not shown). 

Right now, in the secondhand space, there is a slew of competition out to get consumers' attention. As we saw with group discounts, after Groupon's IPO, and later, with meal kits, once a major player in a tech niche goes public, the ability of other companies in the space to raise cash on public markets is (fairly, or not) hitched to the star of the one that makes a public debut. And, that makes the expected IPO of The RealReal ($NASDAQ:REAL) that much more crucial to the rest of the companies in the secondhand sales and consignment space. Right now, Thredup's Google Play App Store Ratings Count far outpace that of The RealReal (not shown). 

The RealReal's strategy of also partnering with brick-and-mortar locations to expand its footprint clearly isn't exclusive to the startup, led by Julie Wainwright, but its strategy of being a first mover to public markets could be a crucial next step in the second sales wars. 

About the Data:

Thinknum tracks companies using information they post online - jobs, social and web traffic, product sales and app ratings - and creates data sets that measure factors like hiring, revenue and foot traffic. Data sets may not be fully comprehensive (they only account for what is available on the web), but they can be used to gauge performance factors like staffing and sales. 

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