Why transaction cost matters
Costs reduce realized return and can turn attractive high-turnover signals into poor strategies. They also affect capacity, portfolio construction, manager comparison, and tax outcomes.
How it is applied
Analysts combine commissions, fees, taxes, spread, market impact, delay, opportunity cost, borrowing, settlement, and foreign-exchange costs using a consistent benchmark such as arrival price.
Portfolio example
A trade pays $1,000 in commissions and loses $9,000 through spread and market impact, producing a $10,000 implementation cost before taxes and financing.
How to interpret it
Low commissions do not imply cheap execution. Implicit costs often dominate for large, illiquid, urgent, or information-sensitive orders.
Limitations and common misconceptions
Benchmark choice changes the estimate, unfilled orders create opportunity cost, and market movement is difficult to separate from impact. Backtests often understate stressed and nonlinear costs.
Sources and further reading
- Trade Strategy and ExecutionCFA Institute