They serve as asset transformers by purchasing primary securities and issuing secondary securities and by purchasing secondary securities and issuing primary securities.

They specialise as brokers between savers and borrowers and they directly control the quantity of outside money in the economy.

They specialise as brokers between savers and borrowers and they serve as asset transformers by purchasing primary securities and issuing secondary securities. 

They serve as asset transformers by purchasing secondary securities and issuing primary securities and they directly control the quantity of outside money in the economy.