YouTube probably generates $16 billion to $25 billion in annual revenue, making the video service big enough to crack the top half of the Fortune 500.

But that’s just a guess. Even though financial analysts on Wall Street think YouTube makes about as much money as the Gap, General Mills or Netflix, the video service’s financial results are a secret. They are lumped in with the rest of Google, an even larger internet company that last year generated $137 billion in revenue.

That secrecy has led to growing frustration among analysts and investors, who will be looking for more details about YouTube when Google’s parent company, Alphabet, reports results for its second financial quarter on Thursday. Three months ago, Alphabet executives pointed to issues with YouTube as a factor in disappointing financial results in the first quarter.

“I think their reticence to provide information borders on paranoia, as if they would be admitting failure if they allowed us to discover whether one of their businesses was performing more poorly than expected,” said Michael Pachter, an analyst at Wedbush Securities.