What do traders mean by a steepener or a flattener?
Duration assumes the whole curve moves by the same amount. Real curves rarely oblige — they twist, and the vocabulary for those twists is one of the most-used dialects on a rates desk.
Curve moves are described in spreads
Practitioners watch spreads between two points, not levels:
- 2s10s — the 10-year yield minus the 2-year yield. If the 2-year is at 4.00% and the 10-year at 4.50%, the spread is +50bp.
- 5s30s, 3M10Y and others follow the same convention.
Steepening means the spread widens. Flattening means it narrows. When a spread goes below zero, that segment of the curve is inverted.
The four named moves
Combine the direction of yields with which end moves more and you get the standard four. Remember that "bull" means falling yields, because falling yields mean rising bond prices.
- Bull steepener — yields fall, the short end falls more. Spread widens.
- Bear steepener — yields rise, the long end rises more. Spread widens.
- Bull flattener — yields fall, the long end falls more. Spread narrows.
- Bear flattener — yields rise, the short end rises more. Spread narrows.
Worked example: the 2-year goes 4.00% → 4.30% while the 10-year goes 4.50% → 4.55%. Yields rose, and the spread went from +50bp to +25bp. Yields up, curve flatter — a bear flattener.
Why this breaks a single duration number
Take two portfolios that both report duration 6. One holds its risk around the 2-year point, the other around the 10-year. In the bear flattener above, the first portfolio is hit by a 30bp move and the second by 5bp. Their profit and loss are nothing alike, yet the risk report said the same number.
Hence key rate durations (or partial DV01s): the sensitivity to a 1bp move at each point on the curve — 2Y, 5Y, 10Y, 30Y. The key rate durations sum back to the total duration; the partial DV01s, being cash amounts, sum back to the total DV01. A twist then appears as a pattern across rows instead of vanishing into a single average. This is the practical answer to the "parallel shift" caveat that has followed you since Unit 2.
Barbell and bullet, one level deeper
In the immunisation lesson the barbell won on convexity. Now look at the same pair through curve risk. Take that duration-8 barbell — 45.7% in the 2-year bond, 54.3% in the 20-year — against a duration-8 bullet, a single bond of about ten years:
- Their money duration splits differently: the barbell carries about 0.9 of its 8 at the short point and 7.1 at the long point; the bullet carries all 8 in the belly.
- If the curve flattens because long yields fall, the barbell's long leg gains more than its short leg loses, and it outperforms the bullet. Note the clause: a flattening driven by short yields rising instead hurts the short leg while the long leg does nothing, and the barbell can underperform. "Flattening" is a label for a relative move, and which end actually moved is what decides the outcome.
- If the curve steepens, the bullet outperforms.
Same duration, same first-order parallel behaviour, opposite curve exposures. "Duration 8" was never the whole description of a position — and now you can say precisely what it left out.
The framing
This is vocabulary and measurement. Naming a move is not calling one, and nothing here is a view on where any curve goes next.
In the data
A 2s10s spread is two points of the same day's curve, subtracted: the 10-year yield minus the 2-year yield. The table has both on two dates a month apart, 25 August and 25 September 2026.
Both yields must come from the same date. A spread built from a 2-year on one day and a 10-year on another mixes a curve move with a level move, and a day on which either point is missing has no 2s10s at all.
Try it now
Using the table in the section above, compute the 2s10s spread on each date in basis points, note whether yields rose or fell overall and which end moved more, and name the move using the four labels.
Sketch the key rate durations of a barbell and a bullet with the same total duration — two tall bars at the ends versus one tall bar in the middle.
Explain in one sentence why "this portfolio has duration 6" is an incomplete risk statement, and what you would ask for next.