Joe Studwell

And what's happened in Africa is that as population has doubled approximately in 25 years, because there's been a bit of economic growth as well, demand for food by value has tripled.

that drives the production of crops.

That's good for ordinary people, smallholder farmers, but particularly in peri-urban areas.

So African agriculture is becoming very bifurcated now between people who are farming around cities

of which there are over 7,000 designated cities in Africa now.

People are farming in those areas because the urban demand is so relentless, so reliable, that you can grow relatively value-added crops, things like tomatoes, instead of what you would have grown in the deep countryside.

And you can sell it and you can make thousands of dollars per hectare and you can afford to buy little pumps and irrigate your soil.

And that will allow you to increase yields.

At the same time as that is going on, there are a lot of places in deep rural Africa where nothing has changed yet.

Yes, it is.

So by value, agricultural output is, as I said, going up over 4% a year.

Population is going up less than 3%.

So population growth is slowing more slowly than it did in East Asia, but it is nonetheless slowing.

And in some African countries, there's a lot of variation.

they're falling but they're coming down from a high level and so this means that it will be some time before africa gets its demographic dividend in other words where it gets a very large share of working people relative to kids and older people to my mind one of the most useful things that

what remains of the aid industry can do in Africa is to put money into female education because that is very closely correlated with lifetime fertility.

I mean, even girls who just do primary school education

have a massively reduced propensity to have lots of kids during their lifetime.

And it's economically very important because the bigger and longer the demographic dividend, the better it is, obviously, for African development.

No, I mean, I think that this is not a perfect science, but to my mind, once you get beyond sort of 50, 60, 70 people per square kilometre on average, obviously your urban densities are massively higher than that, then reducing population growth abruptly in order to maximise the demographic dividend makes sense.