“Individual migrants succeed in capturing the huge productivity gains from migration. But migrants collectively have an interest in precisely what individually is most detrimental: entry barriers.”

Some countries ban immigration entirely; some encourage it; some allow people to settle, but forbid them citizenship. The range in immigration policies spans almost the entire spectrum of possible options, and it seems unlikely all of them are optimal.

Immigration is a controversial topic, in the UK more than most. It’s also one where arguments are generally made with very little evidence on either side: it’s not impossible immigrants are good or bad for the economy/social welfare/tolerance/the social fabric, but it’s hard to know either way. With that in mind, an evidence-based look at immigration is welcome. There are a lot of good sections in Exodus, but unfortunately as whole it also has some weaknesses.

The book basically goes through the costs and benefits to the three groups affected by immigration in turn – migrants, recipient countries, and sender countries. That’s helpful, and Collier makes some insightful points on each. Overall, though, his argument is that the costs and benefits to societies from sending or receiving immigrants are probably small, and the benefits to individual migrants are huge, making at least some migration attractive. At some point, however, there might be too much immigration, given the effect on social fabric and public services.

At the extreme, the possibility of too much immigration seems plausible – purely from a population density perspective, that almost has to be true. The extremely salient question of how much is too much, however, goes entirely unaddressed. Exodus also relies on abstract models to make its points, the stock and trade of economists but something I suspect most other readers will not find convincing. Data is a better approach for this sort of controversial issue, and there the book has much less.

Overall, I think immigration is aching to be addressed in as rigorous, empirically- and evidence-driven a manner as possible, but I’m not sure Exodus is quite there. Presents a useful difference in perspective from usual accounts, but certainly not decisive.