Signals & Measurement
How Mosaic Defines and Calculates Its Odds
Bottom line: every odds figure on Mosaic is a count, not an opinion. It is the share of homes in a defined group that sold within a stated window after a stated starting line. For every figure but one, a sale means a recorded sale of $10,000 or more; the exception is St. Louis County pre-probate, which counts a change of owner (below). This page lists each definition in use today, and the corrections we are making to them. If you have a question about a figure on Mosaic, the answer should be here.
The parts of every odds figure
| Part | What it answers |
|---|---|
| The group | Which homes were counted |
| The starting line | The date the clock starts for each home |
| The window | How long after the starting line we watched |
| The outcome | What counted: a recorded sale, or for one figure a change of owner |
| The count | Homes that sold, divided by homes measured, with its range |
| The comparison | How often a home picked at random sold over the same length of time |
Probate odds, as published today
The group. A probate case filed in St. Charles County or St. Louis County, matched to a home at the address of the person who died, with a known date of death and the property on file. Each case is graded by how long after the death it was filed:
| Grade | Filed after the death | St. Charles County | St. Louis County |
|---|---|---|---|
| Fast filing | under 3 months (under 93 days) | 18.8% (92 of 489) | 12.4% (258 of 2,085) |
| Standard | 3 to 12 months (93 to 364 days) | 15.4% (72 of 468) | 8.7% (190 of 2,194) |
| Flagged | 12 months or more (365 days or more) | 6.1% (10 of 164) | 3.5% (32 of 918) |
The starting line is the date the probate case was filed. The window is 180 days. A sale is a recorded sale of $10,000 or more dated after the filing and no more than 180 days after it. Smaller recorded transfers, such as a $0 deed to an heir, do not count.
The count includes only cases whose full 180 days had passed by August 2, 2026. A newer case is left out until its window closes; it is never counted as unsold. Each county is measured on its own cases, and each record shows its own county's rate.
So "Fast filing, St. Charles County, 18.8%" says: of the 489 St. Charles County probate cases filed under 3 months after the death whose 180 days had passed, 92 had a recorded sale of $10,000 or more within 180 days of the filing. The range printed beside each rate is its 95 percent interval; for that one it is 15.6% to 22.5%.
Pre-probate odds, as published today
A pre-probate record is a death with no probate case yet, so it has no filing date and no grade. Each county carries one provisional group rate, measured differently in each county:
- St. Charles County: 4.0 in 100. Homes matched from an obituary. The starting line is the date of death, the window is 90 days, and a sale is a recorded sale of $10,000 or more. 8 of 201 homes sold (range 2.0 to 7.7), for deaths from November 22, 2025 to May 4, 2026.
- St. Louis County: 6 in 100. Homes still in a deceased owner's name with no probate case as of July 8, 2026. The starting line is that date, the window is the 86 days to October 2, 2026, and the outcome is a change of owner on the county's owner roll, not a priced sale. 22 of 365 homes changed owner (range 4.0 to 9.0).
The two use different windows and different outcomes, so they are not compared with each other or with the probate odds.
The comparison: a home picked at random, on the same clock
Every odds figure sits beside how often a home picked at random in the same county did the same thing over the same length of time. Compare a figure only with the comparison on its own clock.
| Odds figure | Window | A home picked at random, same window |
|---|---|---|
| Probate, St. Charles County | six months | 2.6 in 100 sold |
| Probate, St. Louis County | six months | 2.8 in 100 sold |
| Pre-probate, St. Charles County | 90 days | 1.4 in 100 sold |
| Pre-probate, St. Louis County | 86 days, July 8 to October 2, 2026 | 1.7 in 100 changed owner |
- Sales, both counties. Averaged over monthly start dates from April 2021 to December 2025. In St. Charles County it is every single-family home on the county roll, less probate homes. In St. Louis County it is a random sample of 2,804 single-family homes. Nothing is matched on price, years owned, age or area.
- Change of owner, St. Louis County. 5,370 of the 324,717 single-family homes on the county's owner roll changed owner over the same 86 days the pre-probate figure covers. It counts the same thing the pre-probate figure counts.
A pre-probate figure is never read against the six-month comparison, and never against a probate figure: the windows differ.
What we are correcting
Our own review of these counts found two kinds of home in the probate odds that should not be there.
- Homes the person who died did not own. We find a probate home by the address of the person who died. Some of those homes belonged to someone else, for example a home the person rented. From the next version, a home counts only if the family of the person who died owned it on the starting line. We judge that as of the starting line, never from today's owner, because today's owner of a sold home is the buyer.
- Homes already sold before the filing. Today a home sold between the death and the filing stays in the count as unsold, and a later resale by its new owner can count as a sale. From the next version, a home already sold on the starting line is left out.
Both make the group smaller.
We are also changing how the groups are drawn, so that every group comes from the court record and no case falls in two groups:
- Court-record category, in this order: a surviving spouse is named on the case; independent administration; a will admitted with no administration; a small estate affidavit; any other case type.
- Filing-speed band: under 3 months, 3 to 6 months, 6 to 9 months, 9 to 12 months, and 12 months or more after the death.
Pre-probate will be measured on the same footing as probate, in both counties: from the date of death, on a priced sale, over 180 days, read against the six-month comparison, once enough homes have a full six months behind them.
When this is done, every odds figure will be able to say one sentence: of the homes in this record's group that the family of the person who died owned and had not sold on the starting line, this share had a recorded sale of $10,000 or more within 180 days after the starting line.
How we handle small and surprising numbers
- At least 100 measured homes behind every printed number. Where a filing band has fewer, it is merged with its neighboring band in the same category, and the record says which bands its number covers.
- Size is the only reason to merge. A number with 100 or more homes behind it is printed as measured, even when it reads lower than we expected. We look for the reason in those cases and write it down beside the number. We do not smooth a number to make a table read in order.
How each figure is checked
- Frozen. The homes measured are saved to a fixed file, and the figure is measured from that file. Sales recorded late do not move a published number; they go into the next measurement.
- Recorded. Every figure is entered in our stats ledger with its count, its range, the date its figures run through, and the date by which it will be measured again. The pages on Mosaic print figures from that ledger.
- Fact-checked. Before a figure is printed, a panel of independent AI reviewers, built on different models from the one that drafted it, checks each claim against the source data.
What the odds are not
- A group rate, not a forecast for one house. They count what followed the cases in the record's group, by the definitions above. They do not say whether one house will sell.
- Not a count of investor purchases. A sale is a sale to anyone.
- Not comparable across different windows. A 90-day figure and a 180-day figure count different things.