Storm argues the AI data-centre investment boom is creating a bubble that will be socially and financially expensive when it pops.
Introduction

Can rising asset prices reduce wealth inequality? This paper builds a continuous-time heterogeneous-agent general equilibrium in which entrepreneurs hold risky private capital and traditional savers hold safe assets. Safe-asset expansions—via financial innovation, public debt, or a stable equity bubble—operate through a single pass-through: they lower entrepreneurs’ undiversified risk exposure, compress risk premia, and raise the interest rate.

We employ 68 quarters of data – including from non-public supervisory sources – to study how 17 US and 17 euro-area banks balance the risk of breaching regulatory requirements against the cost of maintaining and speedily restoring “management” buffers. We find that steady-state management buffer targets systematically declined and regulatory risk tolerance (RRT) rose following the Great Financial Crisis, especially at banks experiencing a stronger increase in capital requirements.

Using a novel macro-finance model we infer jointly the equilibrium real interest rate r*, trend inflation, interest rate expectations, and bond risk premia for the United States. In the model r* plays a dual macro-finance role: as the benchmark real interest rate that closes the output gap and as the time-varying long-run real interest rate that determines the level of the yield curve. Our estimated r* declines over the last decade, with estimation uncertainty being relatively contained. We show that both macro and financial information is important to infer r*.