There's a lot of trade between Zambia and the DR Congo.
Makes sense, right? Congo's agricultural sector is a mess. And the southeast corner of the country -- Katanga Province, next to Zambia -- is all mining country, with few farms or ranches anyway. Someone has to feed those miners, and it might as well be Zambia. Food from all over the country flows up the Great North Road to Congo.
But! Most of the trade? is informal. That is to say, it's smuggling. Trucks full of (say) sacks of grain drive north towards the DRC and then park a couple of miles from the border post. Guys on bicycles swarm south across the border, using bush trails that snake well wide of Congo's Customs checkpoint. The truck is unloaded, a sack at a time, and its contents dispersed onto dozens of bikes. Back they go through the bush.
(A while back I blogged about a border post between the DRC and Uganda. There was smuggling around that border post, too, but not so much -- it was in a mountain valley, so smugglers would have to go far around, and through some pretty rugged terrain. The DRC / Zambia border, OTOH, runs through a lot of flat land that's covered in scrub forest... easy to get around.)
Since Zambia doesn't charge export taxes, the Zambian government doesn't get too upset about this. (Congo is losing a lot of money on import duties, but hey: that's Congo's problem.) In fact, Zambia rather likes the current system. The Congolese pay in dollars -- their economy is very dollarized, and anyway nobody's going to take Congolese francs. That's hard currency for Zambia, which is good.
The smugglers in Zambia -- sorry, the "informal traders" -- are actually organized; they've set up their own group, the "association of small cross-border traders" or some such. It's formally registered as a business organization in Zambia, and it barely bothers to conceal its members' activities.
However, Zambia is losing one thing: good statistical information about exactly what is leaving the country. So, a year or two back, the Zambian government contacted the "association", and offered them a modest sum of money to produce a study estimating just what, and how much, was crossing the border from Zambia for the DRC without going through Zambian Customs first. Effectively, the government was saying "Hey smugglers -- we'll give you some money to tell us just what you're smuggling out of the country".
And they did. It's a nice study, too -- very professional.