Evidence suggests that the Colombian interbank funds market is an inhomogeneous and hierarchical network in which a few financial institutions fulfill the role of "super-spreaders" of central bank liquidity among market participants. Results concur with evidence from other interbank markets and other financial networks regarding the flaws of traditional direct financial contagion models based on homogeneous and non-hierarchical networks, and provide further evidence about financial networks' self-organization emerging from complex adaptive financial systems. Our research work contributes to central bank's efforts by (i) examining and characterizing the actual connective structure of interbank funds networks; (ii) identifying those financial institutions that may be considered as the most important conduits for monetary policy transmission, and the main drivers of contagion risk within the interbank funds market; (iii) providing new elements for the implementation of monetary policy and for safeguarding financial stability.

We present a stochastic frontier model with random inefficiency parameters which is able to capture the influence of risk-taking on bank efficiency and that distingues those effects among banks with different characteristics. Cost and profit efficiency are found to be over-and underestimated when risk measures are not accurately modeled. We find that more capitalized banks are more cost and profit efficient, while banks assuming more credit risk are less cost efficient but more profit efficient. The magnitude of these effects vary with bank's size and affiliation. Liquidity is found to affect cost efficiency only for domestic banks. Large and foreign banks benefit more from higher credit and market risk exposures, while small and domestic banks find more advantageous to be more capitalized. We identify some channels that explain these differences and provide insights for macroprudential regulation.

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