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Log-odds and why price moves near the extremes differ

Event contract prices are quoted on a 0 to 100 scale, so it is natural to compare moves in points: up 5, down 3. But points are not equally informative everywhere on the scale. A move from 50 to 55 and a move from 95 to 99 may look similar in size, yet they reflect very different shifts in evidence. Odds and log-odds offer a way to see why. SoftCta literacy uses them as a reading aid, not a trading formula. Pair with implied probability as price, not certainty.

From probability to odds

Odds compare the chance an outcome happens with the chance it does not:

• 50% is 1 to 1.
• 75% is 3 to 1.
• 90% is 9 to 1.
• 95% is 19 to 1.
• 99% is 99 to 1.

Going from 90% to 95% roughly doubles the odds. Going from 95% to 99% roughly multiplies them by five. Near the middle, the same five-point move barely changes the odds. The odds comparator converts between formats if you want to check examples.

From odds to log-odds

Log-odds take the natural logarithm of the odds. On this scale, 50% sits at zero, and the scale stretches symmetrically toward both extremes. Illustrative values:

• 50% → 0
• 55% → about 0.20
• 90% → about 2.20
• 95% → about 2.94
• 99% → about 4.60

A move from 50% to 55% is about 0.2 on the log-odds scale. A move from 95% to 99% is about 1.66 — more than eight times larger. Equal steps on this scale correspond to equal multiplicative changes in odds, which is why statisticians often use it.

Why this matches evidence

In Bayesian updating, a piece of evidence multiplies the odds by a likelihood ratio. On the log-odds scale, that becomes a fixed step regardless of the starting point. The same news could move a contract from 50% to 73% (odds 1 to 1 becoming about 2.7 to 1) or from 90% to about 96% — in points those look different, but the evidential step is the same.

Reading news reactions

When a headline moves one market by 15 points near the middle and another by 3 points near the extreme, the smaller move may represent the bigger update. How news moves implied probability covers reactions more broadly, and the odds move primer lets readers express moves in probability points and cents.

Caution near 0 and 100

Prices near the extremes are also where mechanics matter most. Minimum tick sizes limit how finely prices can express small probabilities. Fees can be large relative to the remaining upside. Collateral tied up in a nearly resolved contract has an opportunity cost. When a market is almost resolved explains why a contract at 97 may not mean the crowd sees a 3% chance of the other outcome.

Symmetry

Log-odds are symmetric: a move from 5% to 1% is the same size as a move from 95% to 99%. Readers sometimes treat long-shot moves as noise while treating favorite moves as meaningful, or vice versa. The scale helps treat both sides consistently.

A worked example

Assume two contracts react to the same report. One moves from 48 to 60; the other moves from 92 to 97. In points, the first move looks larger. In odds, the first goes from about 0.92 to 1.5 (a factor of about 1.6), while the second goes from about 11.5 to 32 (a factor of nearly 3). A reader concludes the second market treated the report as stronger evidence, then checks whether fees and ticks distort that reading. All figures are illustrative; verify live prices.

Failure modes

Treating all point moves as equal. Ignoring mechanics near the extremes. Reading long-shot moves differently from favorite moves. Using log-odds as a trading signal rather than a reading aid. Substantial risk of loss.

Closing SoftCta checklist

• Re-read the venue definition in your own words before reacting to a price.
• Convert prices with fee and spread awareness; verify live cents on the operator.
• Prefer primary settlement sources over secondary headlines and social summaries.
• Treat ChanceWire hubs, movers, and tools as orientation — not order entry.
• Confirm age, location, and product eligibility; SoftCta pages will not suggest location spoofing.
• If clarity is incomplete, watching is a complete SoftCta outcome — no pick-selling urgency required.

SoftCta habits

• Convert prices into odds when comparing moves.
• Expect points near the extremes to carry more evidence.
• Check fees and ticks before interpreting small moves near 0 or 100.
• ChanceWire does not execute trades.
• Verify live prices and rules on the operator.

Where ChanceWire fits

ChanceWire explains probability scales; tools handle conversions. Venues hold live quotes and rules — verify live.

Published 8 October 2026 (Asia/Nicosia). Informational only. Not financial, legal, investment, or tax advice. Rules and fees change — verify on the operator’s site. SoftCta only: ChanceWire does not execute trades. Affiliate disclosure.