Butterfly Trades on the Yield Curve: Trading Curvature Directly

The bullet-vs-barbell vocabulary describes the same idea from a portfolio-construction angle. A BULLET concentrates duration at a single belly point (e.g., heavy weighting in 5-year bonds). A BARBELL splits duration between short and long maturities (e.g., 2-year + 30-year bonds). At the same effective duration, the bullet performs better when the curve curvature increases (belly outperforms) and the barbell performs better when curvature decreases (wings outperform). Active managers express curvature views by tilting between bullet and barbell structures, and butterfly trades make the underlying view explicit in a single position.

Butterfly trades are common around Fed policy-rate decision dates because the BELLY of the curve is most sensitive to changes in the expected path of policy rates over a 3-5 year horizon. A surprise dovish shift can drive the 5-year point down materially while the 2-year (already pricing in near-term cuts) and the 10-year (anchored by long-term expectations) move less. The long-belly butterfly is the natural expression of 'I think the market is underpricing how much the path of policy rates will shift.'

Butterfly trades require careful DV01-weighting to isolate curvature. A common naive mistake is to size the trade in equal NOTIONAL amounts of each leg; this produces a position dominated by whichever leg has the most duration, defeating the purpose. The correct weighting equalizes DV01 on the long-belly leg against the COMBINED DV01 of the two wing legs -- so a 1 bp parallel shift produces zero P&L AND a 1 bp steepener produces zero P&L. Only curvature changes produce P&L. The math is straightforward but easy to mis-implement, and getting it wrong turns a curvature trade into an accidental duration position.

Butterfly trades are LESS commonly discussed in retail commentary than steepeners and flatteners, but they are the standard third tool in any active rates manager's toolkit. The vocabulary -- belly, wings, curvature, butterfly spread -- is part of fluent rates literacy. A retail investor will rarely execute a true butterfly trade (the multi-leg DV01-weighted execution requires futures or active swap access), but understanding the structure is what makes 'the curve is becoming more humped' or 'the belly outperformed' a parseable statement rather than jargon.

Yield-curve butterflies (long belly + short wings, DV01-weighted) isolate curve curvature -- a third dimension of curve shape beyond level and slope. The bullet-vs-barbell vocabulary captures the same idea from a portfolio angle: bullets win when belly outperforms; barbells win when wings outperform. Butterflies require careful DV01-weighting to isolate curvature; naive notional sizing turns the trade into a duration position. The literacy gain is recognizing curvature as a tradeable curve dimension distinct from slope.