Allocating Balance Sheet and Financing Cost

A firm's overall balance sheet — how much it can borrow via repo, how much margin its prime brokers will extend, how much collateral it has to post — is finite and shared across every strategy running simultaneously. A strategy that looks attractive purely on expected return can be a poor use of the firm's resources if it consumes financing far out of proportion to that return, since every dollar of balance sheet it uses is a dollar unavailable to another strategy. Firms therefore allocate capital by comparing strategies on return per unit of financing consumed, not raw expected return alone — a strategy earning 8% but needing cheap, easily-rolled repo financing can be more valuable to the firm than a strategy earning 12% that ties up scarce, expensive balance sheet or requires financing from counterparties with limited capacity.

A relative-value bond strategy financed almost entirely through low-cost general collateral repo, for instance, is usually allocated more balance sheet than a similarly-sized strategy that depends on scarcer special repo or on financing terms that could be pulled back in stress, even if their headline returns look comparable. This framework also shapes which new strategies get greenlit at all: a promising idea that requires financing the firm cannot reliably source, or that would concentrate too much balance sheet with a single counterparty, may be turned down or scaled back regardless of its expected return, simply because the financing itself is the binding constraint.