Bull Flattener

A bull flattener is a yield curve regime where bond prices rise (yields fall) and the curve flattens (the spread between long and short rates narrows). Long-term yields fall faster than short-term yields.

The mechanics:

• Long-term yields drop as investors pile into duration, compressing the term premium
• Short-term yields also fall, but more slowly, as they remain anchored closer to the current Fed funds rate
• The net effect is a flatter curve

Bull flatteners are typically associated with:

• Flight to quality: during market stress, investors buy long-duration Treasuries for safety, pushing long-end yields down sharply
• Quantitative easing: central bank purchases concentrate in longer maturities, compressing long-end yields
• Pension and insurance demand: liability-driven investors buy the long end to match their obligations
• Deflation fears: expectations of sustained low inflation make long-duration bonds more attractive

Bull flatteners are favorable for existing long-duration holders, whose positions appreciate in value. They are also the mirror image of the bear steepener: where the bear steepener reflects rising term premium, the bull flattener reflects its compression.

The regimes tool tracks all five regimes — Bull Steep, Bull Flat, Bear Steep, Bear Flat, Consolidation — and their historical frequencies.