Ledger of Empires

Ask most people what the interest rate is, and they'll tell you a single number the policy rate their central bank set at its last meeting. It's the number that leads the news, the number politicians get asked about, the number every mortgage advertisement quietly references. It is also, increasingly, not the number that actually determines what a household pays to borrow. There's a second rate sitting underneath it, one that almost nobody outside a bank's treasury desk tracks, and over the last few years it has quietly become more important than the one everybody watches.

Two rates pretending to be one

The policy rate is a wholesale price. It's what a commercial bank pays, roughly, to borrow overnight from the central bank, or what it earns on reserves parked there. It's a powerful signal and it does move borrowing costs throughout the economy but only through a chain of intermediate steps, each of which can add or subtract a little friction. Between the central bank's decision and the number on your mortgage statement sits a bank's funding costs, its assessment of your risk, its appetite for lending relative to its capital position, and this is the part that's changed its competition for deposits.

For most of the last two decades, that chain was fairly tight. Banks were flush with cheap deposits, funding markets were calm, and the spread between the policy rate and what an ordinary borrower actually paid stayed narrow and predictable. You could look at the policy rate and get a good estimate of the mortgage rate just by adding a fixed margin. Central bankers liked this world because it meant their main lever worked more or less as advertised.

That world has gotten noisier. Deposit competition has intensified as digital banks and money-market funds make it trivially easy for savers to move cash toward whoever's paying the best rate that week. Banks that used to enjoy cheap, sticky deposits now have to compete for funding in a way that pushes their own costs up independent of anything the central bank does. The result is a widening and increasingly volatile spread between the policy rate and the effective rate households and small businesses actually face.

Why this matters more than it sounds

If the spread were just wider, that would be a nuisance but not a structural problem you'd adjust your mental model and move on. The issue is that the spread has become less predictable, and unpredictability is much more corrosive to planning than a consistently higher number.

A household deciding whether to fix a mortgage rate for five years is implicitly making a bet not just on where the policy rate goes, but on where the spread goes a variable that used to be close to background noise and is now doing real work. A small business owner assessing whether to take on debt to expand faces the same problem, except with less sophisticated tools to think it through and much less patience for surprises.

For a central bank, this is uncomfortable in a specific way: it means the transmission mechanism they're relying on to cool or stimulate the economy has become less reliable exactly when precision matters most. Raise the policy rate by half a point expecting a certain amount of tightening, and you might get more tightening than intended if bank funding stress happens to spike at the same time, or less if banks are sitting on excess capital and absorb the increase rather than passing it through. Central banking has always involved some amount of pushing on a string, but the string used to be shorter and stiffer.

What I watch instead

When I'm trying to get a real read on financing conditions in Norway or anywhere, honestly I've stopped anchoring primarily on the policy rate announcement and started paying closer attention to bank funding spreads and deposit competition data, boring as that sounds compared to a rate decision with a press conference attached. It's a less exciting number to track, and it doesn't come with a press conference, but it tells you something the headline rate increasingly can't: what credit conditions actually feel like to the person applying for a loan, as opposed to what the central bank intended them to feel like.

There's a useful analogy here to weather forecasting. The policy rate is like the regional temperature forecast useful, directionally right, worth knowing. The effective borrowing rate households face is more like the temperature in your specific garden, affected by microclimate factors the regional forecast was never built to capture. You wouldn't dress for the day based on the regional number alone if you had access to the local one. I'd argue the same logic applies to how households and businesses should think about financing costs, and to how policymakers should think about how much confidence to place in their main lever.

A modest proposal for how we talk about rates

None of this is an argument against policy rates as a tool they remain the most powerful and legible instrument a central bank has, and abandoning that legibility in favor of something more complicated would be a mistake. But I think central banks and financial commentators alike could do more to narrate the spread itself as a variable worth watching, rather than treating it as an implementation detail beneath notice.

A rate decision that comes with a clear statement about what's happening to bank funding costs and deposit competition would tell households and businesses far more about what to actually expect on their next loan than the headline number in isolation. We spend enormous public attention on twenty-five basis point decisions and almost none on the plumbing that decides how much of that twenty-five basis points actually reaches anyone. I don't think that balance is right, and I don't think it will correct itself without someone in the room asking the less glamorous question out loud.