Long-duration Treasuries — the 10-year and 30-year — are usually the first place financing stress shows up when a capital-intensive buildout runs hot, because they're the instruments most sensitive to two things at once: how much new debt supply the market has to absorb, and how durably higher that debt's coupon needs to be to attract buyers.
The four inputs
The Long Duration Stress Index (LDSI) averages four normalized signals:
- 10Y yield momentum — the pace and direction of recent 10-year yield moves.
- 30Y yield momentum — the same, for the long bond, which tends to react more sharply to duration risk repricing.
- Term premium increase — the compensation investors demand for holding long-duration risk, isolated from inflation expectations and the real rate.
- Treasury auction weakness — softer demand at auction (lower bid-to-cover, more left with primary dealers) as an early liquidity signal.
Why this matters for AI specifically
AI infrastructure investment is being financed substantially with debt. As that debt issuance grows, it competes with Treasury issuance for the same pool of long-duration capital. If foreign and domestic buyers start demanding a higher term premium to absorb both at once, it shows up here before it shows up in AI-linked credit spreads directly — which is why LDSI is tracked as a leading indicator, not a lagging one.
0–30 is normal, 30–60 is a warning worth watching weekly rather than daily, and above 60 is stress — the point where financing conditions themselves start to constrain the buildout, independent of whether the underlying AI business case is sound.