What was one effect of the trans-saharan caravan trade during the thirteenth and fourteenth centuries

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.

Complementary goods. they go together, thats why one price increase and the others demand increases