P URVEYORS OF BALLOT papers, indelible ink and polling booths will do well in Africa this year. No fewer than 18 countries are to hold general elections. Not all will be free and fair, but in many the stakes are high. In Ethiopia the popularity of Abiy Ahmed, a reformist prime minister, will be tested at the polls for the first time. Burkina Faso, which is battling jihadists, will hold only its second poll since Blaise Compaoré, a long-serving dictator, was overthrown in 2014. And in Ghana President Nana Akufo-Addo faces a tight race for a second term.

Given the stakes, one might expect voters to turn out in droves. Yet in Africa fewer tend to vote than elsewhere, even if the election is not rigged. More surprisingly it is the young, rich and urban who tend to stay away from the polls. Why?

In the West the rich vote more than the poor. But Kimuli Kasara of Columbia University and Pavithra Suryanarayan of Johns Hopkins University, who surveyed voting patterns in poor countries, many of them in Africa, found that the poorest fifth of citizens tended to vote more assiduously than the richest fifth. One possible reason for rich Africans’ lack of motivation to vote is that no matter who wins, they are unlikely to be taxed more. Rates may rise, but tax collection is ineffective. In sub-Saharan Africa tax revenue averages 17% of GDP compared with 34% in the OECD , a club of mostly rich countries.