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Expectancy per unit time

Edge per trade multiplied by how many trades you get, which is the figure that actually determines account growth.

Two systems: A earns plus 0.5R per trade and trades twice a month; B earns plus 0.15R per trade and trades daily. Per trade, A is more than three times better. Per year, A earns 12R and B earns roughly 37R. B compounds faster despite the weaker-looking signal.

Compute it as expectancy x trade frequency over the same window, and adjust for capital occupancy: a trade holding capital for ten days at plus 0.4R yields 0.04R per day, while one holding for two days at plus 0.2R yields 0.10R per day. That comparison is the justification for time-stop rules.

The limit on the logic is cost and capacity. More trades means more slippage-budget and more chances to deviate from process, and both scale with frequency while the edge does not. Beyond some rate, added frequency subtracts.

Related: expectancy-per-trade, trade-frequency, time-stop, slippage-budget

See it drawn

Original diagrams for the ideas on this page. Illustrative, not real market data.

The spread of outcomes behind an expectancyA histogram of forty trades: a tall block of small losses on the left, a low spread of larger wins on the right, and a line marking the average outcome.NUMBER OF TRADES051024 LOSSES, AVG −$20016 WINS, AVG +$600EXPECTANCY +$120−$400−$200$0+$200+$400+$600+$800PROFIT OR LOSS PER TRADEexpectancy = (40% × $600) − (60% × $200) = +$120 per trade
Expectancy: the average trade. Forty trades sorted by outcome: 24 small losses and 16 larger wins. Weighting each side by how often it happens gives the average result per trade, marked here by the dashed line at +$120.
Slippage on a market orderA buy order clears four price levels, so the average price paid is worse than the price first quoted.Buy 1,000 shares at marketpricesell orders resting (bar length = size)20.04300 shares20.03200 shares20.01200 shares20.00300 sharesnothing resting at 20.02order sweeps up the bookaverage fill 20.02SLIPPAGE0.02 a share$20.00 in totalintended 20.00Each level fills at its own price; the average is what you really paid.
Slippage on a market order. You click at 20.00, but only 300 shares are resting there, so the rest of the order fills at 20.01, 20.03 and 20.04. The average price paid is 20.02, and that two-cent gap is slippage.

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