A good place to start when valuing a TV network is to look at revenue per subscriber. You can break that down further, seeing how much it makes from a direct subscriber versus an affiliate one, for example. The average network receives a retransmission fee of around $2.10 per affiliate station subscriber per month – but those numbers don’t always correlate with viewership. For example, CBS earns about the same per subscriber as drama specialist AMC, even though its programming gets many more viewers – perhaps suggesting CBS could boost its profits by selling to people directly.

That’s an assumption based on what the company could do, though. To directly compare network stocks as they are, investors look at EBITDA multiples. ViacomCBS, at the time of writing, trades at about 6.5x its earnings, compared to 16x for Fox – either indicating that ViacomCBS is significantly undervalued or that Fox has greater growth prospects. Affiliate stable Nexstar, however, trades at 8x its earnings – and given what we discussed last session about its future prospects, that might make CBS seem appetizing.

The really tricky thing when comparing network stocks, is finding adequate comparisons. Thanks to conglomeratization there are few companies today that represent a simple bet on a TV network: ABC and NBC both make up just a small portion of their parent companies’ revenues. And even with those that are closer to “pure-play” investments – like ViacomCBS and Fox – you’re investing in other things too (ViacomCBS owns a book publisher, while Fox, for some reason, owns a loan marketplace).

It’s also hard to compare the TV networks themselves. CBS’s value is underpinned by long-running procedurals, while Fox’s relies on its controversial but popular news output. While both are TV shows, they have very different revenue drivers. Still, as the TV industry shifts to a direct-to-consumer model, you might argue that entertainment is worth more than current affairs: you’re probably more likely to pay for 456 old Law & Order episodes than 456 old news broadcasts. And then there are the new ways that TV channels will have to monetize their content in the brave new world of streaming…

The takeaway: Investors look at EBITDA multiples to compare TV networks’ stocks, but finding suitable comparisons can be tricky.