“SBM has this proxy for food inflation called the Jollof Index,” he explains, referring to the tomato-based rice dish, popular across West Africa. “We calculate the average cost of making a pot of jollof rice for a family of five. It was just under 4,000 naira at the start of 2016, and now it’s around 10,000 naira [$22, £18] – so it’s more than doubled in five years.”