My theory is milk. Breakfast cereal is designed to be covered in milk, but compared to North America and Western Europe, milk and milk products are far less popular in most of the world. I think I remember reading that there's even a biological reason, ethnic Europeans have some enzyme for digesting milk (and cheese etc) that others lack.

This would imply that other milk-drinking Western countries would also eat a lot of breakfast cereal. And indeed it's something I notice when I go back from China to Belgium or the UK.

(Disclaimer: I haven't been to the US, so perhaps Americans like breakfast cereal even more than Europeans)

American here, I grew up on breakfast cereal (for better or worse). Cereal seems to be one of those things that exploded in variety and marketability in the U.S. I've never seen anything like an American cereal aisle in any of the other countries I've been to anywhere in the world.

What I find really interesting though is how that's slowly starting to change as other countries start to adopt more of the quick-eat consumerist culture similar to the U.S. What's more fun is that the local solutions to snacks and cereals are usually very interesting and designed for local tastes.

The first time I went to Europe, 20 some odd years ago there really was a slim selection, mostly variants of Muesli mixes. When I was in Russia in the 90s, I really wanted some breakfast cereal and there was a big effort to get milk and some corn flakes. In Germany I had more selection, but not hugely.

The first time I went to Korea about 15 years ago it was the same.

More recently I notice the amount and selection of breakfast cereals is exploding on those countries. Most of my experience has been in Korea, and there are now full-on cereal aisles with an entire list of different products. Not as many as the U.S. but definitely getting there.

So what's fun it that not only do I get to eat all the American varieties, but as other countries add other cereals to their cultural inventories, I get to try and enjoy those as well.

Yes, Scandinavian genetics are more likely to express code for lactase and so less likely to develop lactose intolerance.

US also subsidies milk production to keep prices reasonable, which may have a side effect of increasing the amount consumers will pay for associated products like cereal.

It's possible the margins are not as high, or they are not as high vs other more popular products. It could be a combination of multiple factors at play. Certainly if nobody was buying cereals in the US the high margins would not be enough to sustain shelf-space spending, so that's a valid point.

I suspect that US producers have higher margins on sugary products because of corn subsidies.

I'd say you're correct, but in a slightly more indirect way than many might assume (they might read it as, gov. gives money to company, therefore company has more money -- but they still compete with each other on price, so that doesn't totally make sense). But because corn is subsidized, the food is cheap on a $/calorie basis, which means customers can be less price sensitive, because it's all easier and cheaper than eating a non-corn-based meal. We see this reflected in the fact that cereal (a very generic term for a certain type of staple) is emphatically _not_ a commodity. People have types they like more -- so they can compete on something other than price, which lets profits go up. A good line of research to verify is to compare cereal demand elasticity to e.g. meat, where there are variations people like more than others, and it's semi-interchangeable, but because of price people treat it largely as a commodity.