Suppose that an MFI loses $1000 per year in bad debts due to client AIDS deaths, before attempting any risk management. This is the inherent risk.
Suppose the MFI partners with a local government antiretroviral programme and local AIDS service organisation providing education and VCT. As people access treatment, the deaths reduce, and the following year the losses are only $400. This is the residual risk.
The $600 that was saved by implementing the risk control is effectively the controlled risk.