Before revision:  We develop an explicit expression for the matrix of asset holdings which minimizes market inefficiency , and characterize it in terms of two key sufficient statistics: the banks' systemic significances and the statistical moments of asset shocks  .
After revision:  We develop an explicit expression for the matrix of asset holdings which minimizes market inefficiency , and characterize it in terms of two key drivers, the banks' systemic significances and the statistical moments of asset shocks .