Module 1: Trading Math: Expectancy

The Three Levers: Win Rate, Average Win, Average Loss

5 min readLesson 1 of 10

This lesson examines the three primary variables influencing trading profitability: Win Rate, Average Win, and Average Loss. Understanding the interplay of these variables is fundamental to maximizing positive expectancy. Expectancy is the average profit or loss per trade over a large sample size. A positive expectancy indicates a profitable trading system.

Expectancy Formula Review

Recall the Expectancy formula:

$\text{Expectancy} = (\text{Win Rate} \times \text{Average Win}) - (\text{Loss Rate} \times \text{Average Loss})$

Where:

  • $\text{Win Rate}$ is the percentage of winning trades.
  • $\text{Loss Rate} = 1 - \text{Win Rate}$.
  • $\text{Average Win}$ is the average profit from winning trades.
  • $\text{Average Loss}$ is the average loss from losing trades.

These three variables—Win Rate, Average Win, and Average Loss—are the levers traders manipulate to achieve and maintain positive expectancy.

Lever 1: Win Rate

Win Rate is the proportion of trades that close profitably. It is expressed as a percentage or a decimal.

$\text{Win Rate} = \frac{\text{Number of Winning Trades}}{\text{Total Number of Trades}}$

A higher Win Rate generally contributes to higher expectancy, assuming other variables remain constant. However, a high Win Rate alone does not guarantee profitability. A system with an 80% Win Rate can be unprofitable if its Average Loss significantly outweighs its Average Win.

Impact of Win Rate

Consider a trading system with:

  • Average Win: $200
  • Average Loss: $100

If Win Rate = 60%: $\text{Expectancy} = (0.60 \times $200) - (0.40 \times $100) = $120 - $40 = $80$

If Win Rate increases to 70%: $\text{Expectancy} = (0.70 \times $200) - (0.30 \times $100) = $140 - $30 = $110$

A 10% increase in Win Rate, with fixed Average Win and Average Loss, increases expectancy by $30 per trade.

Traders improve Win Rate through enhanced entry criteria, better market timing, and superior trade management. This often involves tighter stop-loss placement or more precise profit-taking levels.

Lever 2: Average Win

Average Win is the mean profit generated from all winning trades.

$\text{Average Win} = \frac{\text{Total Profit from Winning Trades}}{\text{Number of Winning Trades}}$

Increasing Average Win significantly impacts expectancy. This often involves letting winners run, scaling out of positions, or targeting larger price movements.

Impact of Average Win

Consider a trading system with:

  • Win Rate: 50%
  • Average Loss: $150

If Average Win = $100: $\text{Expectancy} = (0.50 \times $100) - (0.50 \times $150) = $50 - $75 = -$25$ (unprofitable)

If Average Win increases to $200: $\text{Expectancy} = (0.50 \times $200) - (0.50 \times $150) = $100 - $75 = $25$ (profitable)

A $100 increase in Average Win, with fixed Win Rate and Average Loss, shifts the system from losing $25 per trade to gaining $25 per trade.

Strategies to increase Average Win include identifying and trading higher probability setups with larger profit targets, or employing trailing stops to capture extended moves.

Lever 3: Average Loss

Average Loss is the mean loss incurred from all losing trades.

$\text{Average Loss} = \frac{\text{Total Loss from Losing Trades}}{\text{Number of Losing Trades}}$

Minimizing Average Loss is crucial for profitability. This involves strict risk management, precise stop-loss placement, and adherence to predefined maximum loss limits.

Impact of Average Loss

Consider a trading system with:

  • Win Rate: 50%
  • Average Win: $200

If Average Loss = $150: $\text{Expectancy} = (0.50 \times $200) - (0.50 \times $150) = $100 - $75 = $25$

If Average Loss decreases to $100: $\text{Expectancy} = (0.50 \times $200) - (0.50 \times $100) = $100 - $50 = $50$

A $50 decrease in Average Loss, with fixed Win Rate and Average Win, increases expectancy by $25 per trade.

Traders reduce Average Loss by setting tighter stop-loss orders, cutting losses quickly, and avoiding emotional decisions that lead to holding losing positions too long.

Interplay of the Levers: A Concrete Example

A day trader executes 100 trades on ES futures contracts. Each contract has a point value of $50.

Trade Data:

  • Winning Trades: 45
  • Losing Trades: 55
  • Total Profit from Winning Trades: $13,500
  • Total Loss from Losing Trades: $8,250

Step 1: Calculate Win Rate and Loss Rate $\text{Win Rate} = \frac{45}{100} = 0.45 \text{ or } 45%$ $\text{Loss Rate} = 1 - 0.45 = 0.55 \text{ or } 55%$

Step 2: Calculate Average Win $\text{Average Win} = \frac{$13,500}{45} = $300$

Step 3: Calculate Average Loss $\text{Average Loss} = \frac{$8,250}{55} = $150$

Step 4: Calculate Expectancy $\text{Expectancy} = (0.45 \times $300) - (0.55 \times $150)$ $\text{Expectancy} = $135 - $82.50$ $\text{Expectancy} = $52.50$

This system has a positive expectancy of $52.50 per trade.

Now, let's analyze how adjusting one lever impacts overall expectancy.

Scenario 1: Improve Win Rate

The trader implements a new entry filter. This increases the Win Rate from 45% to 50%, while Average Win and Average Loss remain constant.

$\text{New Win Rate} = 0.50$ $\text{New Loss Rate} = 0.50$ $\text{Average Win} = $300$ $\text{Average Loss} = $150$

$\text{New Expectancy} = (0.50 \times $300) - (0.50 \times $150)$ $\text{New Expectancy} = $150 - $75$ $\text{New Expectancy} = $75$

An increase of $22.50 per trade ($75 - $52.50).

Scenario 2: Increase Average Win

The trader adjusts profit targets, aiming for larger moves. This increases Average Win from $300 to $350, while Win Rate and Average Loss remain constant.

$\text{Win Rate} = 0.45$ $\text{Loss Rate} = 0.55$ $\text{New Average Win} = $350$ $\text{Average Loss} = $150$

$\text{New Expectancy} = (0.45 \times $350) - (0.55 \times $150)$ $\text{New Expectancy} = $157.50 - $82.50$ $\text{New Expectancy} = $75$

An increase of $22.50 per trade ($75 - $52.50).

Scenario 3: Decrease Average Loss

The trader tightens stop-loss orders. This decreases Average Loss from $150 to $100, while Win Rate and Average Win remain constant.

$\text{Win Rate} = 0.45$ $\text{Loss Rate} = 0.55$ $\text{Average Win} = $300$ $\text{New Average Loss} = $100$

$\text{New Expectancy} = (0.45 \times $300) - (0.55 \times $100)$ $\text{New Expectancy} = $135 - $55$ $\text{New Expectancy} = $80$

An increase of $27.50 per trade ($80 - $52.50).

The Trade-offs

Adjusting one lever often

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