Why is the amount of child porn growing?

I doubt porn-related child abuse is growing.

NCMEC says that reports of child porn are growing, but that could easily be reports per posting, postings per image, or images per activity. NCMEC just *counts* reports, which are either a member of the public clicking a "report" button or an algorithm finding suspicious content. They acknowledge that a significant part of the rise in from broader deployment of such algorithms.

Similarly, the fraction of porn-producing activities which involve traumatic abuse is unclear. And is likely declining, judging by common anecdotes of sexual teenage selfies. I realize anecdotes are weak evidence at best, but producing such images is becoming easier, and puberty ages are dropping, so I'll stand by my weak claim.

NCMEC sites IWF as saying that "28% of CSAI images involve rape and sexual torture", but I cannot find a matching statement in IWF's report. The closest I find is "28% of these reports [from members of the public] correctly identified child sexual abuse images," but IWF seems to regard any sexualized imagery of an under-18-year-old as "abuse", even if no other person is involved.

In any case, the IWF report is from 2016 and clearly states that "self-produced content" is increasing, and the share of content which involves children under 10 is decreasing (10 is an awkward age to draw a line at, but it's the one they reported on). Likely these trends continued into 2018.

On the meta level, I note that NCMEC and IWF are both organizations whose existence depends on the perceived severity of internet child porn problems, and NYT's business model depends on general dislike of the internet. I don't suspect any of these organizations of outright fraud, but I doubt they've been entirely honest either.

I’d only be surprised if this was a different trend from the total amount of pornography available online. The internet allows people to coordinate better and increase the demand for lots of products and industries - including illegal and immoral ones - especially where the product is images.

My suspicion is that we are seeing a "one time" increase due to better ability to create and share child abuse content. That is, my guess is the incident rate of child abuse is not much changing, but the visibility of it is because it's become easier to produce and share content featuring the actions that were already happening privately. I could imagine some small (let's say 10%) marginal increase in abuse incentivized by the ability to share, but on the whole I expect the majority of child abuser are continuing to abuse at the same rate.

Most of this argument rests on a prior I have that unexpected large increases like this are usually not signs of change in the thing we care about, but instead changes in secondary things that make the primary thing more visible. I'm sure I could be convinced this was evidence of an increase in child abuse proportionate with the reported numbers, but I think it far more likely lacking such evidence that it's mostly explained by increased ease producing and sharing content only.

Also most (!) of this stuff circulates through FB Messenger, so plans to encrypt Messenger end-to-end have a dark implication. From the Times piece:

And when tech companies cooperate fully, encryption and anonymization can create digital hiding places for perpetrators. Facebook announced in March plans to encrypt Messenger, which last year was responsible for nearly 12 million of the 18.4 million worldwide reports of child sexual abuse material, according to people familiar with the reports.