In this video, Fool analyst Matt Koppenheffer examines the past, present, and future of bank net interest margins. He outlines why margins improved when the Federal Reserve dropped interest rates and why net interest margins are now under pressure. The future may bring more pressure and banks of all sizes are vulnerable. Non-interest income may be enough to offset losses elsewhere, but diligence is recommended.

Matt Koppenheffer owns shares of Bank of America. The Motley Fool recommends Wells Fargo. The Motley Fool owns shares of Bank of America, Citigroup, and Wells Fargo. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.