How often do home values change?

Value moves every day. The reports do not.

If you check your home's estimated value every morning with your coffee, I have news. The house did not change overnight. The number did.

Value is what a typical buyer would pay for your home in the current market. That market moves whenever buyers and sellers agree on a price. A new listing down the street, a drop in mortgage rates, a bidding war two blocks over: each one shifts the picture a little.

The problem is that we only see those shifts after the fact. Contracts take weeks to close. Closings take time to be recorded and collected. Then the data has to be analyzed and published. By the time a headline says "home values rose," the market that made it happen is often a few months old.

So there are really two answers to this question. Value changes constantly. The measurements of value change on a schedule, and they run behind.

How often the big indexes update

Here is how two of the most cited sources work.

FHFA House Price Index. The Federal Housing Finance Agency publishes its index every month. Every three months it releases a fuller quarterly report, in February, May, August and November, which includes the monthly data. The index is built from single-family sales with mortgages bought or backed by Fannie Mae or Freddie Mac. FHFA says it generally receives data on new loans with a lag of about two months, and it revises recent figures as more data comes in.

S&P CoreLogic Case-Shiller. Case-Shiller also publishes monthly. It is a repeat sales index, meaning it compares the sale prices of the same houses over time. It is reported with about a two-month delay and uses a three-month moving average. A release at the end of July reflects the three months ending in May.

Zillow also publishes a monthly market report on typical home values. Different sources use different sales, methods and time windows, which is why two headlines in the same week can disagree. Neither one is lying. They are just measuring different slices of the past.

Monthly reports, in other words, are the norm. Real-time reports are not.

Why the numbers lag the market

The biggest delay is built into the deal itself. A sale that closes this week was usually negotiated weeks before. Inman's explainer on Case-Shiller notes that those transactions typically went to contract one to three months earlier. So a late-July Case-Shiller release can reflect deals struck from about February to April.

Stack the delays together and a reported index can describe a market that is three to five months old by the time you read it. In a calm market, that does not matter much. In a market that is turning, it matters a lot.

It is like driving by looking only in the rearview mirror. You will see the road you just took very clearly. The curve ahead, less so.

Revisions add another wrinkle. FHFA notes that historical values get revised as new data arrives, especially for the most recent periods. The first number you see is not always the final number. Think of it like the first estimate from a contractor. It is a starting point, and it tends to change once the walls are open.

How an appraisal handles a moving market

An appraisal values the home as of one date, called the effective date. A value as of any later date is a different question, and it takes a new assignment to answer it.

Because comparable sales close over a period of months, the appraiser has to check whether the market moved between each sale's contract date and the effective date. Fannie Mae's guidance says time adjustments, or the lack of them, must be supported by evidence, preferably other sales and contracts. Home price indexes and paired sales are acceptable support too.

This is where I spend a lot of my time. I read the market in real time. That means looking at the most recent window the data can support, such as the last 30 or 45 days, and checking it against longer periods. Pending sales and active listings help, because they show what buyers are doing now, before it shows up in any index.

A national index is useful context. Your neighborhood, your price range and your type of home can be moving a different way.

How to keep track of your own home's value

1. Check monthly, not daily. Monthly data is what the major sources publish. Daily swings in an online estimate are mostly the model, not the market.
2. Watch your own segment. Look at recent sales of homes like yours, in your area, from the last few months.
3. Watch pendings and new listings. They are the earliest signal of where closed sales are heading.
4. Compare year over year. Spring and fall patterns can make month-to-month numbers look scary when they are normal.
5. Remember the lag. When a headline reports a change, ask what months it actually covers.
6. Get an appraisal when it counts. For a sale, a refinance, an estate or a divorce, an evidence-based appraisal tells you the value as of a specific date and shows the sales behind it.

Your house does not need daily weigh-ins. It needs an honest checkup when a decision is on the line.