Percentage Points vs Percent, and Why It Matters
A move from 2% to 3% is one percentage point and a fifty percent increase. Confusing the two produces headlines that are technically true and completely useless.
This is a small point that causes an outsized amount of confusion, and it is worth getting right permanently because prediction market data is full of both quantities.
The distinction
A market moves from 2% to 3%.
- The change is one percentage point.
- The change is a 50% increase.
Both statements are true. They describe the same move. Used carelessly, the second one makes trivial movements sound dramatic.
Now consider a market moving from 60% to 61%. That is also one percentage point, and it is a 1.7% increase. The same one-point move, described in relative terms, can be "up 50%" or "up 1.7%" depending only on where it started.
Why this matters for market data
Any list of "biggest movers" computed in relative terms will be dominated by markets in the low single digits, because that is where relative changes are largest. A market going from 1 cent to 2 cents is up 100% and has told you almost nothing. Meanwhile a market going from 44 to 52 is up 18% in relative terms and is a genuinely significant repricing.
This is why this site ranks movement in points and then weights it by how unusual that point-move is for the market in question. Relative change is not used for ranking at all, because it systematically surfaces the least informative markets. Telling a significant move from noise covers the method.
Where percentage change is the right tool
It is not that relative change is always wrong. It is the right measure for anything denominated in money.
Return on a position. Buying at 40 and selling at 44 is a 10% return. That is the number that matters to a position, and it is correctly relative.
Volume growth. Volume doubling is meaningfully "up 100%".
Costs. A fee of half a cent on a 40-cent contract is 1.25% of capital, which is the honest way to express it.
The rule is simple. Probabilities move in points. Money moves in percent.
The odds framing, which is better still
There is a third framing that is more informative than either, and it is worth having in your toolkit.
A price of 50% is even odds. A price of 2% is about 49-to-1 against. A price of 3% is about 32-to-1 against. So the move from 2% to 3% shortened the odds from 49-to-1 to 32-to-1, which is a substantial revision — much larger than the "one point" framing suggests and differently sized from the "50%" framing.
Near the middle, the odds framing and the points framing agree. Near the extremes they diverge sharply, and the odds framing is the one that tracks how much evidence arrived. This is the intuition behind why prices near 1c and 99c behave differently.
How to describe a move accurately
The clearest formulation names the level and the change together:
"Moved from 44 to 52, up eight points."
Not "up 18%". Not "up eight percent". Eight points, from 44 to 52. Anybody reading it knows exactly what happened.
If you want to convey significance as well:
"Moved from 44 to 52, up eight points, against a typical daily range of two."
That sentence contains everything. It is the format this site's movers board is built to communicate, because the alternative is a leaderboard of one-cent markets.
The reporting failure this produces
You will see this in coverage of prediction markets constantly: a headline announcing that markets "doubled" the chance of some outcome, where the underlying move was from 4% to 8%. Technically accurate. The actual information — that a long shot got slightly less long — is not what the reader takes away.
The reverse failure exists too. A move from 70% to 85% gets reported as "up 21%", which understates a change from 2.3-to-1 on to 5.7-to-1 on. Fifteen points at that level is a large revision.
Neither error is malicious. Both come from reaching for the relative framing by default because that is how we talk about prices of things.
The habit
When you read a prediction market number anywhere, ask which of the two it is. When you write one, use points for probabilities and say the word "points" out loud. It is a two-second discipline that eliminates an entire class of misunderstanding.
Next
Decimal, fractional and American odds, converted covers the other arithmetic people reach for, and where the conversions hide the vig.
Educational content only. Nothing here is financial advice, a solicitation, or an offer to trade. Prediction markets can move against you and a position can lose its entire value. Where this guide describes a difference between venues it describes a theoretical cross-market edge in observed prices, which is not a profit: fees, spreads, capital lockup, transfer time and differing settlement rules all come out of it first.
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