Implementation Shortfall
Computes the implementation shortfall of a buy order, André Perold's concept that measures the gap between the return of a paper portfolio executed instantly at the decision price and that of the actually executed portfolio with all costs. It separates the execution cost (price impact and commissions) from the opportunity cost of the shares that went unfilled. The result comes in money, percentage and basis points, always as a cost (positive is worse). Enter the decision price, the execution price, the quantities, the commissions and the final price.
Result
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Implementation Shortfall
Computes the implementation shortfall of a buy order, André Perold's concept that measures the gap between the return of a paper portfolio executed instantly at the decision price and that of the actually executed portfolio with all costs. It separates the execution cost (price impact and commissions) from the opportunity cost of the shares that went unfilled. The result comes in money, percentage and basis points, always as a cost (positive is worse). Enter the decision price, the execution price, the quantities, the commissions and the final price.
The gap between the plan and reality
When a manager decides to buy a stock, there's a price at that instant: the decision price. But between deciding and executing, the market moves, the order causes impact, part of it may not even fill. Implementation shortfall, André Perold's concept, measures everything lost along the way: the difference between the ideal portfolio, executed for free and instantly, and the portfolio that actually came out.
It decomposes the cost into two revealing parts. The execution cost combines price impact (you bought higher than the decision price) and commissions. The opportunity cost measures what you left on the table on the shares you couldn't buy while the price rose. Together, they show the true cost of turning a decision into a position.
Enter the decision price, the average execution price, how many shares were ordered and how many filled, the commissions and the final price of the unfilled shares. The tool returns each component and the total, in money, percentage and basis points, always as a cost: positive means worse than ideal. The example covers a buy order.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.