🏦 Deposits & Fundingβ€ΊModule 22

Deposit betas: theory, estimation, and real-world tracking

Deposits & FundingModule 22 of 111
1,942 words9 min read

Deposit betas measure the sensitivity of your deposit costs to market rate changes. A beta of 0.60 means: for every 100 basis points the market moves, your deposit costs move 60 basis points. This single number shapes your net interest margin, your ALM hedge ratios, your funding strategy, and ultimately your earnings stability.

Yet deposit betas are maddeningly hard to estimate and unstable. Historical betas from 2019 are worthless in 2023. Banks that estimated betas on pre-2022 data took massive margin surprises when rates rose and deposits repriced faster than model assumptions. The 2022–2024 rate cycle revealed this starkly: regional banks that had betas of 30–40% in calm markets discovered they had effective betas of 80–90% when spreads widened and competition intensified.

This module teaches you how to estimate deposit betas rigorously, how to track them in real time, and how to build the estimation logic that works across rate cycles. By the end, you'll have a working framework that captures structural changes in your deposit franchise without requiring you to rebuild your model every 18 months.

Why Betas Matter

One simple example: Assume you have $100B in deposits, a 5-year loan portfolio averaging 4.5% yield, and a 50% asset-to-deposit ratio in shorter-term debt (CDs, wholesale funding). Your net interest margin is:

NIM = (Loan Yield Γ— Loan Assets + Short-Debt Yield Γ— Short Debt) / Total Assets - (Deposit Beta Γ— Market Rate Change Γ— Deposit Base / Total Assets)

If the Fed raises rates 100 bps and your deposit beta is 0.40, your deposit costs rise 40 bps on averageβ€”a $400M earnings impact per year. If your beta is actually 0.70 (as it was for many banks in 2023), the hit is $700Mβ€”a $300M surprise miss. On a typical regional bank's pretax income of $1.5–2B, that's a 15–20% earnings shock.

This is why accurate beta estimation is not an academic exercise. It directly drives your interest rate risk hedging strategy, your funding cost forecasts, and your earnings guidance to investors.