Count an episode, then divide by time
The observed rate is
where is the number of completed episodes whose closing timestamps fall in the reporting window and is the length of that window in the chosen time unit. Orders cancelled without execution do not count as completed round trips. An episode still open at the end does not count yet; one opened before the window does count if it closes inside it under this closing-date convention.
| Calendar month | Jan | Feb | Mar | Apr | May | Jun | Total |
|---|---|---|---|---|---|---|---|
| Completed round trips | 1 | 3 | 0 | 2 | 4 | 2 | 12 |
March is part of the observation window even though nothing closes. Dividing only by active months would answer a different question. The average also does not say that the strategy completes two trades every month.
Other clocks answer other questions
A daily rate needs an explicit denominator: calendar days, exchange trading sessions or hours when the strategy was enabled. Include idle periods that belong to the chosen exposure window. Use timestamps and a stated time zone for boundary events. Do not convert calendar months into trading days using an unstated calendar.
| Quantity | What it measures |
|---|---|
| Average holding period | How long positions remain open; parallel positions and idle time prevent a general reciprocal relationship with trade frequency. |
| Portfolio turnover | Trading activity measured by amounts relative to a stated portfolio-value basis; a trade count omits size. |
| Sampling frequency | How often data are observed. A model can inspect every observation without placing an order. |
| Model-run frequency | How often the model evaluates its rules, which may produce no trades. |
The historical rate is a description of this sample. Treating it as a future event-arrival rate requires an additional statistical model and assumptions about stability and clustering. It does not establish a constant arrival intensity or independent trade outcomes.
Higher frequency can increase execution demands and costs. It supplies no performance advantage by itself: compare strategies using their event conventions, position sizes, costs, risks and net results, rather than ranking them by activity alone.
Sources
- Rishi K. Narang, Inside the Black Box: A Simple Guide to Quantitative and High-Frequency Trading, 2nd edition (2013), Chapter 3, p. 55, “Run Frequency.” Explains model-run cadence and its trade-offs with trading costs and noisy signals.
- SEC staff, Rule 605 FAQs, Question 27, updated 1 April 2026. Distinguishes an order from its partial executions in execution-quality reporting; the round-trip convention above is stipulated for this article.
- SEC, Concept Release on Equity Market Structure (2010), pp. 45–46. Historical discussion of HFT characteristics and definition difficulties.