Weekly return
How much did a market change over a week, and why does one number hide how it got there?
In plain words
Weekly return is the percentage change from a market's opening price at the start of the week to its closing price at the end. It compresses seven days of trading into one figure, ignoring everything that happened between those two points.
Why it matters
A weekly return tells you the net result, not the journey. Two weeks with identical returns can differ completely in how deep the price fell before recovering, how large the intraday swings were, and how much stress a position endured along the way. Risk is carried on the path, not on the endpoints.
In a real week: ETH, week of 3 September 2018
In the week of 3 September 2018, ETH fell from an open of 295.51 to a close of 195.81, a weekly return of -33.74%. That single number understates the week's interior: the price touched a high of 296.62 at the week open, fell to a low of 185.02 on 9 September, and spanned a total range of 60.32%. The best day gained 0.62%, while the worst day lost 19.86%. A position sized from the closing figure alone would have missed both the depth of the drop and the size of the largest single hourly move, 6.46%, recorded on 9 September.
A common mistake
Reading a weekly return as a smooth, steady move. The market may have fallen much further midweek, or swung widely, before settling at the closing price.