My Sunday column looks at one facet of child trafficking, the child pornography industry. This was largely eliminated by the early 1990’s and then exploded with the Internet, but it’s mostly hidden in peer-to-peer networks and the “dark web” so that few people are aware just how odious it is.

My column has some numbers, but they don’t go to the heart of the question because we just don’t know how many kids are exploited in child pornography. Indeed, the industry is so deep underground that the data are pretty weak and uncertain. All we know is that it’s big and very ugly.

One other point. Look, I know this stuff is hard to read; it’s also hard to report, and hard to write. Whenever I write about painful topics like human trafficking, my readership falls. But our squeamishness is one reason it continues; we have to break the taboos and talk about these issues as a step toward making progress. So I’d welcome your suggestions for how we go about tackling this industry.