In Malawi, like in many other developing countries, the bicycle is king for transportation and cargo carrying.
The bikes we saw a few years ago were primarily Chinese or Indian manufactured. They looked like the old 3 speeds once widely available in the states. On the back of nearly every one was a sturdy steel rack, many of the racks were customized for load carrying. In 4 weeks in Malawi, I only saw one bike without a rack. He was probably riding it to the shop to have a rack put on it.
Regular people used bike taxis to get around. The passenger would sit on a padded cushion on the rack, hook his or her feet onto the axle and hold on. It was an amazing balancing act. The way that the Malawians moved such incredibly awkward, bulky and heavy things on their heads and bicycles gives me great respect for developing world athleticism.
They were probably all one speeders. Gears or changing hubs would probably break, and become costly or difficult to repair. Even the western style mountain bikes that I saw had the derailleur bypassed or removed and the chain shortened.
Often the bikes would have a simple set of tools tied onto the frame for emergency repair. In Mulanje I met up with an amazing man using a scratch built welder to fix bicycles and other steel devices.