安联投资团队以「牛顿摆」作为隐喻，指出美国信用市场的风险并未消失，而是在投资等级债券（IG）、高收益债券（HY）与私募信贷之间不断转移。表面上利差收窄、市场平静，但底层基本面正在恶化，价格与风险已在每个环节脱钩。

投资等级债券目前利差仅约75个基点，低于历史合理水准，但信用品质已走软（利息覆盖率约6.3倍、净杠杆约2.7倍）。一旦发生「堕落天使」降评，指数型投资人被迫抛售至流动性更低的高收益市场，可能引发远超信用品质变化的利差波动。高收益债券看似稳健，实则是因最弱的借款人已迁移至杠杆贷款和私募信贷，造成组成效应的假象。

私募信贷中，借款人结构性更弱（杠杆5至7倍、覆盖率仅1至2倍），但因采用估值平滑机制，净资产价值看似稳定。实物支付利息（PIK）比例已从2023年初的4.3%倍增至8.9%，贷方接管规模也大幅攀升。安联警告，一旦市场承压，风险将回流至公开高收益市场，使其成为私募信贷的「非自愿避震器」，利差可能因流动性抛售而大幅扩大。

Allianz's investment team uses the metaphor of a Newton's Cradle to argue that US credit risk has not disappeared but has migrated across investment-grade bonds, high-yield bonds, and private credit. Beneath calm surfaces and tight spreads, fundamentals have weakened at every link in the chain, with prices decoupling from underlying credit quality through different mechanisms.

IG spreads sit near historic tights at roughly 75 basis points despite softening credit metrics, propped up by yield-hungry, price-insensitive demand rather than sound fundamentals. Fallen-angel downgrades could force index-constrained selling into a smaller HY market, amplifying spread moves. Meanwhile, HY appears resilient largely due to a composition effect: the weakest borrowers have migrated to leveraged loans and private credit, pushing BB-rated bonds above 50 percent of the index and CCC to a 20-year low.

In private credit, structurally weaker borrowers (leverage of 5–7x, coverage of 1–2x) are masked by appraisal-based NAV smoothing. Payment-in-kind interest has roughly doubled to 8.9 percent, and lender takeovers have surged. Allianz warns that under stress, illiquid private credit and crowded HY positions cannot be unwound quickly, so investors sell liquid public HY first regardless of its fundamentals—making junk bonds the involuntary shock absorber for the broader credit complex.