Want to know if a marketing platform will work for your brand? Check the stock market.

The insight here is pretty simple. If a marketing platform is generally effective, many businesses will use it. If many businesses use it, the company will make a lot of money. If the company makes a lot of money, its stock will go up.

Stock price times share count will get you market capitalization, which is what investors think a business is worth overall. And you can use a company’s market capitalization as a quick reference point on whether ads work on its platform.

The ad-supported companies with the highest marketing capitalization are:

  • Google ($1.14 trillion)
  • Amazon ($958 billion, though this is mostly AWS)
  • Meta ($442 billion)

What do all of these have in common? Ads work on these platforms at scale, at least much of the time.

Want to know if Pinterest or Snapchat ads will work for you? Well, they don’t seem to be working that well for most others:

  • Pinterest ($17 billion)
  • Snap ($16B)

Oh, and Elon Musk bought Twitter for $44 billion but most people think it would trade at less than $20 billion now if it were still public.

I once spent a lot of time thinking about Taboola and Outbrain, so-called “native” ad platforms. Their combined market cap is now $1.4 billion.

Look, am I saying you should never try running ads on platforms with a small market cap? I wouldn’t go that far. I’ve had some success with native ads and seen others who’ve had success on Pinterest or Snap. And there might be deals to be had on super small platforms like Rokt.

But in general, the stock market’s pretty efficient. If small ad platforms were crushing it for a lot of brands, they would be much bigger companies than they are. There’s a reason everyone talks about Google, Facebook, and (increasingly) Amazon so much. They work at scale for way more brands than the small guys.