When it comes to internet shutdowns, African nations are among the world’s worst violators.

From Ethiopia in the east to Algeria in the north, Cameroon in the center and Zimbabwe in the south, countries are regularly cutting off connectivity for extended periods than any other region globally, the 2018 Transparency report from Facebook shows. The report monitors the accessibility of Facebook’s services worldwide and identifies internet disruptions that affect their availability.

Cameroon holds the record for overseeing Africa’s longest internet blackout. Starting from January 2017, connections in the Anglophone Southwest and Northwest regions has either been completely off or slowed down for extended periods. Following protests against linguistic, political, and economic discrimination, the Francophone-dominated government blocked the internet or access to certain social media platforms in a bid to stifle dissent and calls for secession. Facebook data shows the country blocked access for more than 40 weeks between January 2017 and June 2018.

Internet disruptions have been imposed for longer periods in Chad, the Democratic Republic of Congo, and Togo, while shorter disruptions have been recorded in Egypt, Mali, and The Gambia.

Across Africa, even though there are fewer shutdowns than before, governments are getting increasingly sophisticated by targeting social media networks and not entire internet infrastructures, which are vital to economic growth. As such, the blocks have taken aim at Facebook products—including WhatsApp, Instagram, and Facebook Messenger—and also Twitter, Viber, Skype, and YouTube.

That doesn’t mean the blocks aren’t undermining productivity and costing countries jobs and income. In fact, cutoffs affect not only formal government revenues but also the informal sector. “Grey” economies are vital in Africa and the global south, given the number of people employed and the level of cash transactions. (Governments including Uganda and Zambia also recently introduced internet taxes, which critics say will shrink public discourse.)

Digital rights advocates are fighting the shutdowns in court, highlighting how the restrictions violate rights to free expression and information. Those efforts can sometimes prove futile: After waiting for more than two years to get a court hearing on why Uganda shut the internet during its February 2016 elections, activists failed to get their petition heard last week. The judge had called in sick.