Maintaining an outsized asset portfolio exposes the central bank’s balance sheet to significant financial risks, particularly when interest rate cycles turn upward.

When inflation forces a central bank to raise its short-term policy interest rate, the market value of its fixed-rate, long-term bond holdings drops. This shift creates dual financial pressures:

Net Income Spread = Bond Portfolio Yields - Interest Paid on Excess Commercial Reserves

If the interest paid on commercial bank reserves rises above the yield earned on historical bond portfolios, the central bank faces an operational loss. While a central bank cannot go bankrupt in a conventional sense because it prints fiat money, extended operational losses can require state treasury support, potentially complicating political relationships and testing institutional independence.