CookbookResearch and civic lifeNo. 51
A forecasting studyone prediction-market question, researched like a thesis
See it in know.sh
ForecastingNo. 14
Will Measure R pass?Port Calder’s transit tax, 3 November 2026
9 sections, 3,410 words, about 15 minutes, revised Sunday 27 September.
The question. Will Measure R, a half-cent sales tax for thirty years to fund bus rapid transit and the Line 2 extension, pass on 3 November 2026? It resolves Yes if the county’s certified count shows more than half the votes cast on it as Yes. Election night does not settle it; certification does.
Chance Measure R passes: the market against my forecast, each Sunday
| Week ending | Market | My forecast |
|---|---|---|
| 2 Aug | 52% | 45% |
| 9 Aug | 55% | 45% |
| 16 Aug | 54% | 45% |
| 23 Aug | 61% | 52% |
| 30 Aug | 58% | 52% |
| 6 Sep | 60% | 52% |
| 13 Sep | 66% | 57% |
| 20 Sep | 60% | 55% |
| 27 Sep | 62% | 55% |
The market’s implied probability, noted each Sunday evening. Port Calder, Measure R and every figure here are invented.
Chance Measure R passes: the market against my forecast, each Sunday
| Week ending | Market | My forecast |
|---|---|---|
| 2 Aug | 52% | 45% |
| 9 Aug | 55% | 45% |
| 16 Aug | 54% | 45% |
| 23 Aug | 61% | 52% |
| 30 Aug | 58% | 52% |
| 6 Sep | 60% | 52% |
| 13 Sep | 66% | 57% |
| 20 Sep | 60% | 55% |
| 27 Sep | 62% | 55% |
Values: Chance of Yes
The value axis runs from 30% to 80%.
Reference line at 50%: Even.
Marked at 23 Aug: Chamber endorses.
Marked at 13 Sep: Poll: 54% Yes.
Marked at 20 Sep: No campaign starts.
Source: The market’s implied probability, noted each Sunday evening. Port Calder, Measure R and every figure here are invented.
```element chart
{
"type": "line",
"caption": "Chance Measure R passes: the market against my forecast, each Sunday",
"dimension": "Week ending",
"labels": [
{
"label": "2 Aug"
},
{
"label": "9 Aug"
},
{
"label": "16 Aug"
},
{
"label": "23 Aug"
},
{
"label": "30 Aug"
},
{
"label": "6 Sep"
},
{
"label": "13 Sep"
},
{
"label": "20 Sep"
},
{
"label": "27 Sep"
}
],
"series": [
{
"name": "Market",
"values": "52, 55, 54, 61, 58, 60, 66, 60, 62"
},
{
"name": "My forecast",
"values": "45, 45, 45, 52, 52, 52, 57, 55, 55"
}
],
"units": "%",
"measure": "Chance of Yes",
"axisTitles": true,
"min": 30,
"max": 80,
"markers": true,
"highlight": "My forecast",
"annotations": [
{
"axis": "y",
"at": "50",
"label": "Even"
},
{
"axis": "x",
"at": "23 Aug",
"label": "Chamber endorses"
},
{
"axis": "x",
"at": "13 Sep",
"label": "Poll: 54% Yes"
},
{
"axis": "x",
"at": "20 Sep",
"label": "No campaign starts"
}
],
"source": "The market’s implied probability, noted each Sunday evening. Port Calder, Measure R and every figure here are invented."
}
```I sit seven points under the market. The gap is the base rate: in midterm Novembers, only two of the county’s five transit taxes have passed.
Sections
- 1The question and how it resolvesQuestion
- 2Base rates: the county and the regionEvidence, keySix of nine county transit taxes since 2000 passed; two of five in midterm years.
- 3For: the Harbour Institute pollEvidence
- 4For: the Chamber of Commerce endorsementEvidence
- 5For: bus ridership is backEvidence
- 6Against: the taxpayers’ campaignEvidence
- 7Against: Measure K, 2018EvidenceThe last attempt failed with 48.6 per cent.
- 8The evidence, weighedInsight, key
- 9Forecast logDecision
ForecastingWill Measure R pass?
8of 9
The evidence, weighed
Insight, key section, 1 note, 7 sources, 480 words
Each piece of evidence has its own section with its source. Here they are side by side, weighted by how much each should move a forecast that starts from the base rate.
Evidence on Measure R, as of 27 September
| Evidence (section) | Leans | Weight |
|---|---|---|
| County midterm record: 2 of 5 transit taxes passed (2) | No | High |
| Region since 2010: 19 of 31 transit taxes passed (2) | Yes | Medium |
| Harbour Institute poll, 11 September: 54% Yes, 12% undecided (3) | Yes | High |
| Chamber of Commerce endorsement, 21 August (4) | Yes | Medium |
| Bus ridership above its 2019 level since March (5) | Yes | Low |
| Taxpayers’ association campaign, from 20 September (6) | No | Medium |
| Measure K failed with 48.6% in 2018 (7) | No | Low |
High moves the forecast several points; low, one or none. The poll counts for less than its size suggests: 12 per cent undecided with five weeks to go.
Evidence on Measure R, as of 27 September
| Evidence (section) | Leans | Weight |
|---|---|---|
| County midterm record: 2 of 5 transit taxes passed (2) | No | High |
| Region since 2010: 19 of 31 transit taxes passed (2) | Yes | Medium |
| Harbour Institute poll, 11 September: 54% Yes, 12% undecided (3) | Yes | High |
| Chamber of Commerce endorsement, 21 August (4) | Yes | Medium |
| Bus ridership above its 2019 level since March (5) | Yes | Low |
| Taxpayers’ association campaign, from 20 September (6) | No | Medium |
| Measure K failed with 48.6% in 2018 (7) | No | Low |
High moves the forecast several points; low, one or none. The poll counts for less than its size suggests: 12 per cent undecided with five weeks to go.
```element table
{
"caption": "Evidence on Measure R, as of 27 September",
"columns": [
{
"label": "Evidence (section)",
"align": "left"
},
{
"label": "Leans",
"align": "left"
},
{
"label": "Weight",
"align": "left"
}
],
"rows": [
[
"County midterm record: 2 of 5 transit taxes passed (2)",
"No",
"High"
],
[
"Region since 2010: 19 of 31 transit taxes passed (2)",
"Yes",
"Medium"
],
[
"Harbour Institute poll, 11 September: 54% Yes, 12% undecided (3)",
"Yes",
"High"
],
[
"Chamber of Commerce endorsement, 21 August (4)",
"Yes",
"Medium"
],
[
"Bus ridership above its 2019 level since March (5)",
"Yes",
"Low"
],
[
"Taxpayers’ association campaign, from 20 September (6)",
"No",
"Medium"
],
[
"Measure K failed with 48.6% in 2018 (7)",
"No",
"Low"
]
],
"notes": "High moves the forecast several points; low, one or none. The poll counts for less than its size suggests: 12 per cent undecided with five weeks to go."
}
```Where that leaves me. The poll and the endorsement outweigh the midterm record, but not by much. 55 per cent, not the market’s 62.
Forecast log: every change to my number, and why
Forecast, 20 September
55% Yes
The No campaign launched with a clear message about the tax’s thirty-year length. Down two points.
Forecast, 13 September
57% Yes
Replaced by Forecast, 20 September
The first independent poll, 54 per cent Yes. Up five, not more: 12 per cent undecided.
Forecast, 23 August
52% Yes
Replaced by Forecast, 13 September
Business opposition sank Measure K in 2018; the Chamber backing this one removes it.
Opening forecast
45% Yes
Replaced by Forecast, 23 August
The county’s midterm record, 2 of 5, nudged up by the region’s 19 of 31.
The October poll
Move to 60% if Yes leads by eight or more
Written down before the poll, so the result cannot talk me into more.
Also considered Hold at 55% if the lead is under five
Forecast log: every change to my number, and why
Forecast, 20 September
✓ Decided 20 September
Choice: 55% Yes
Reason: The No campaign launched with a clear message about the tax’s thirty-year length. Down two points.
Forecast, 13 September
⊘ Superseded 13 September
Choice: 57% Yes
Replaced by: Forecast, 20 September
Reason: The first independent poll, 54 per cent Yes. Up five, not more: 12 per cent undecided.
Forecast, 23 August
⊘ Superseded 23 August
Choice: 52% Yes
Replaced by: Forecast, 13 September
Reason: Business opposition sank Measure K in 2018; the Chamber backing this one removes it.
Opening forecast
⊘ Superseded 2 August
Choice: 45% Yes
Replaced by: Forecast, 23 August
Reason: The county’s midterm record, 2 of 5, nudged up by the region’s 19 of 31.
The October poll
○ Open
Choice: Move to 60% if Yes leads by eight or more
Reason: Written down before the poll, so the result cannot talk me into more.
Also considered: Hold at 55% if the lead is under five
```element decisions
{
"caption": "Forecast log: every change to my number, and why",
"decisions": [
{
"title": "Forecast, 20 September",
"status": "decided",
"date": "2026-09-20",
"choice": "55% Yes",
"reason": "The No campaign launched with a clear message about the tax’s thirty-year length. Down two points."
},
{
"title": "Forecast, 13 September",
"status": "superseded",
"date": "2026-09-13",
"choice": "57% Yes",
"reason": "The first independent poll, 54 per cent Yes. Up five, not more: 12 per cent undecided.",
"supersededBy": "Forecast, 20 September"
},
{
"title": "Forecast, 23 August",
"status": "superseded",
"date": "2026-08-23",
"choice": "52% Yes",
"reason": "Business opposition sank Measure K in 2018; the Chamber backing this one removes it.",
"supersededBy": "Forecast, 13 September"
},
{
"title": "Opening forecast",
"status": "superseded",
"date": "2026-08-02",
"choice": "45% Yes",
"reason": "The county’s midterm record, 2 of 5, nudged up by the region’s 19 of 31.",
"supersededBy": "Forecast, 23 August"
},
{
"title": "The October poll",
"status": "open",
"choice": "Move to 60% if Yes leads by eight or more",
"reason": "Written down before the poll, so the result cannot talk me into more.",
"alternatives": [
{
"option": "Hold at 55% if the lead is under five"
}
]
}
]
}
```How it works
Will Port Calder’s transit tax pass in November? The market says 62 per cent. Your study starts from the county’s record, weighs each poll and endorsement in a section of its own with sources, and logs every change to your own number, so when the count is certified you can score your reasoning, not just your luck.