Expected value

Also called EV · +EV

The average result of a trade if it could be repeated forever — your probability times the payout, minus the all-in cost.

For a contract paying one dollar, expected value per contract is simply your probability minus the all-in cost, where cost already includes fees. Per dollar staked it is that edge divided by the cost. A positive number means the trade is worth taking repeatedly. It means nothing more than that, and the three limits are worth stating in full.

Positive expected value does not guarantee profit — not on one trade, and not over any finite run of them. Variance is the entire experience of trading these markets, and a genuinely good edge can lose for a long time. Second, the estimate is only as good as your probability, which is a judgment rather than a measurement; being systematically five points overconfident turns a modest edge into a modest loss. Third, an expected value computed off a last-trade price is an expected value for a trade you cannot execute.

Expected value also says nothing about size. That is the separate question Kelly answers, and it is why a large computed edge on a market with no depth behind it is not an opportunity — it is a number.

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Definitions describe how Polymarket and Kalshi behave and how WhaleTracks models them; venue rules and fee schedules can change, so confirm anything you size a position on with the venue itself. WhaleTracks is informational analytics, not financial advice. Past performance does not guarantee future results.