How a Local Housing Market Works

SStock and flow

Start with the distinction between stock and flow. The stock is every dwelling that exists: houses, duplexes, condominiums, apartments, whether occupied, empty or half-finished. It is enormous, and it changes very slowly. New construction in a settled city adds a small increment each year, and demolition removes a smaller one. For practical purposes the stock you have this year is the stock you will have next year.

The flow is the part of the stock that is actually for sale at any given moment. It is a tiny slice, and unlike the stock it moves fast. A market that looks starved of housing may simply have a stalled flow: the dwellings exist, but their owners have no reason to sell. Almost everything people call a shortage is a flow problem wearing the costume of a stock problem.

Keeping the two apart explains a great deal. Building more houses works on the stock, slowly, and its effect on this season's prices is faint. Anything that changes owners' willingness to move works on the flow, and its effect is immediate.

IInventory and absorption

Inventory is the count of dwellings listed for sale. Absorption is the rate at which buyers take them off. Divide the first by the second and you get months of supply, which is the single most useful number in local housing and the one least often quoted.

A market with a few months of supply is one where a reasonable house, correctly priced, will find a buyer without a long wait. A market with many months of supply is one where the same house sits. The number is not a forecast; it is a description of the current queue, and it changes direction faster than prices do. Prices are the last thing to move, because sellers resist reductions and buyers resist increases, and both resist by simply not transacting.

This is why volume turns before price does. When conditions change, the first visible effect is that fewer sales happen. Only after the queue lengthens do asking prices follow.

WWhy markets are local

Housing markets are local because the goods are fixed in place. A buyer who wants to be near a particular school, a particular workplace or a particular lake cannot substitute a cheaper house forty miles away, because the thing being bought is the location as much as the building. That makes the effective market for any given house quite small, sometimes only a few streets wide.

National statistics average across thousands of these small markets and can therefore be true and useless at the same time. It is entirely ordinary for a national index to report a decline while a particular set of blocks is competitive, or the reverse. The city scale is already too coarse: within a single city, older districts with small lots and newer districts with large ones behave like separate economies.

The practical consequence is that anyone trying to understand a market should narrow the frame until the houses in it are genuinely substitutable for one another, and then look at inventory, absorption and time on market within that frame.

SSeasons

Northern markets have a pronounced season. Listings rise in late winter and early spring, peak through early summer, and thin sharply through late autumn. Buyers follow roughly the same curve, because moving households prefer not to move children mid-year and prefer not to move furniture through snow.

Because both sides move together, the season affects volume much more than price. The autumn market is not necessarily cheaper; it is smaller. Fewer houses are available, but the buyers still looking in November tend to be the ones who have a reason to complete, which is why a house that has failed to sell all summer often sells quickly once the casual traffic disappears.

WWhat a market cannot tell you

A market average is a statement about many houses and no house in particular. Two buildings on the same block, built in the same year to the same plan, can be worth materially different amounts because one has a sound foundation and the other does not. Aggregates describe the weather; they do not describe the roof over any individual head.

Treat market description as context. It tells you whether you are negotiating in a crowded room or an empty one. It does not tell you what any specific building is worth, and no page on this site attempts to.