The rate lock-in effect is the supply story

The clearest explanation for constrained resale inventory is not demographics or construction. It is that a large share of owners hold mortgages at rates far below what they would pay today.

The arithmetic

An owner with a $400,000 balance at 3% pays materially less each month than the same balance at 6.5%. Moving means giving up the old rate and financing the next house at the new one.

Even a lateral move — same price, same size — means a substantially higher payment. So the rational decision for millions of households is to stay, and they have.

What it does to the market

Resale supply stays tight even when demand softens, because the sellers are not participating.

New construction gains share, because builders can buy down rates as an incentive in a way an individual seller cannot.

Renovation spending rises. Households that would have traded up improve instead, which shows up in home-improvement retail long before it shows in listings.

When it unwinds

Slowly, and through life events rather than through rates — jobs, divorce, death, growing families. Those forced moves are a fairly steady share of transactions each year and they set a floor on supply.

A meaningful decline in mortgage rates would release it faster, but the gap has to close substantially before the arithmetic changes for most holders.

General information, not personalised financial advice.

Reported at HousingWire; analysis ours.