The secular decline in interest rates and the rise of shadow banks

Over the past two decades, shadow banks have significantly expanded their share of residential mortgage lending, even surpassing pre-financial crisis levels. This surge is often attributed to post-crisis regulatory changes and improvements in shadow banks’ technology. In this paper, we document a new driving force: the persistent decline in interest rates. When interest rates are high, cheap deposit funding provides banks with a significant competitive advantage against shadow banks relying on wholesale funding. As interest rates plummet and approach the zero lower bound, banks lose this advantage, experience a squeeze in their net interest margin, leading to diminished profitability, weaker growth, and cost-cutting measures such as branch closures. By contrast, shadow banks are able to gain market share. We test this mechanism using a shift-share empirical design based on differences in historical bank balance sheet composition. We find that banks more vulnerable to falling interest rates contracted lending as a response to lower profitability while also scaling back non-interest expenses on their branches. This created a fertile environment for non-banks to expand in areas with banks exposed to declining interest rates.