Information asymmetries make it difficult for banks to assess accurately whether specific entrepreneurs are able and/or willing to repay their loans. This leads to implicit interest rate ceilings, i.e. banks refuse to increase their interest rates beyond this ceiling as this would lower their net returns. Although the maximum interest rate increases as the size of enterprises decreases, such ceilings nonetheless constrain the banks’ ability to set interest rates at a level that would enable them to cover costs. If transaction costs are high, the total costs associated with granting small and medium-sized loans will exceed the maximum average return which the banks can earn by issuing such loans. For this reason, banks do not lend to small and medium-sized enterprises, and, as a consequence, these businesses have no access to formal sector loans. Because micro and small enterprises have a very high RoI, it is worthwhile for them to rely on expensive informal loans to finance their operations, at least until they reach a certain size. Once they have reached this size, however, it does not make economic sense for them to continue taking out informal credits, and thus they face a growth constraint imposed by the credit market. Medium-sized enterprises earn a lower RoI than small ones, which is why borrowing in the informal credit market is not a worthwhile option for them. Moreover, they do not have access to credit from formal financial institutions, and are thus excluded from obtaining any kind of financing in either of the two credit markets. As the result of free, unregulated market forces we get a stable equilibrium in which the credit market is segmented into an informal (small loan) segment, a formal (large loan) segment and, in between, a non-market (medium loan) segment.