The next half-century is likely to be very bloody

Most researchers – if not quite a consensus – think the world is getting more peaceful. Steven Pinker's book puts this view in its broadest form. I am not an expert on violent conflict, but I disagree. (I don't feel bad about expressing my amateur's opinion. Experts on violent conflict, unlike, say, experts on quantum physics, are not necessarily much better able to make predictions than the rest of us, and the wisest of them would admit that.)

I expect the next half-century to have more, and perhaps bigger, wars, massacres and genocides than the first half of the twentieth century.

My prediction is based on a simple two step theory of modern history:

1. Economic growth makes people rich;
2. Then they fight over the spoils.

In the 19th century, Europe got rich. European nation-states then fell to fighting over the spoils of empire. This led to two world wars, which some historians redescribe as a single "thirty years' war". There were also many episodes of violence within states, including genocide.

In the late 20th century, the whole world started to get rich. This means there will be bigger fights.

Specifically, as the US gets less powerful, there will be a period without a "hegemon", a world policeman. When the teacher leaves class, the children start to misbehave.

Technological progress also enables people to kill each other faster, when they want to, and this is likely to make some conflicts very bloody.

There are three main risks of large-scale violence.

• Big interstate wars between growing powers, or between rising and status quo powers. So, US-China or China-India.

The risk of these is low because these countries have nuclear weapons, which makes war very costly, and they are also large and complex enough to have reasonably sane leadership and bureaucracies, which lowers the risk of them doing something stupid. On the other hand, if it happened, it would be catastrophic.

• Middle-sized interstate wars, or large-scale civil wars in large countries. 

We have this now in the Middle East: part of the reason is surely the US snoozing on the job after its unfortunate adventure in Iraq. When the countries involved have large populations, and war is not limited or localized, the number of casualties can get very large. There is not much reason to think that nuclear weapons will make conflict less likely, if they are in the hands of incompetents or madmen. (Remember they have been used twice already.)

• Massacres and genocide.

Economic growth benefits some groups more than others, and as Amy Chua and before that Donald Horowitz pointed out, this can cause violence. There are many vulnerable groups in the developing world. Probably the single biggest one is India's Muslims. These are a minority; there is a well-established political party which uses anti-Muslim hate to get ahead, and which is now running the country; and there is a history of violence between Muslims and Hindus, including the million killed during Partition. Also, the vulnerable population is huge – 180 million.

There is no deep social science insight or data analysis behind my belief. (The 2 step theory is influenced by the book Violence and Social Orders, from the economic historian Douglas North and his coauthors. Their theory is much subtler than my dumbed-down version, though.) It is just a personal view. I am not very sure of it, because I am aware of my profound ignorance, and of my many previous mistaken predictions.

Still, I would like other people to worry about it more: I hope the experts will adduce better reasons to show I am right or wrong. This is not because we can do much to stop mass violence, but because it would be wise to prepare for it.

There is a third step of history: after people have fought to a standstill, they settle down and continue to get rich. This seems to have happened in the developed West. I hope it will happen in the whole world. Until then the ride will probably be bumpy.