Desk Slang · Core
Bull Flattener
A bull flattener is the curve flattening as yields fall, usually because the front end rallies more than the long end into easier policy or a growth scare.
Definition
Flatten = spread narrower. Bull = yields down, fronts leading. Typical of late-cycle cut pricing. A bear flattener is the hawkish twin: fronts sold more than longs.
Why it matters
Mortgage and bank NIMs, and any 2s10s asset swap, live on which flatten you are in.
Case
Late 2018 and parts of 2019: cut pricing bull-flattened 2s10s. 2022 hikes bear-flattened it first.
How to read it
Again: name the pair and the outright direction. Four curve words (bull/bear × steep/flat) exist because P&L needs all four.
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