An index a reader cannot reconstruct is worth nothing to them, so this one has no hidden weights and no judgement calls. Five components, each a single disclosed count from the filing record, each scored as a percentile rank against the previous 120 months. The composite is their unweighted mean.

• Issuance: SPAC IPOs that priced in the month, from the final prospectus on file. The most direct read on whether sponsors can raise.
• Pipeline: Registrants filing an S-1 or a confidential draft in the month. Leads issuance by roughly one to two quarters, so it reads intent rather than execution.
• Deal formation: Vehicles that disclosed a definitive business-combination agreement, counted from the merger filing rather than from press coverage.
• Completion balance: Of the vehicles that resolved over the trailing 6 months, the share that closed a combination rather than returning the trust. Unlike the other components this is already a rate, so it is used directly.
• Attrition: Vehicles that wound up in the month, from the delisting and deregistration record. Scored inverted: more wind-ups means a colder read.

Because the comparison window spans the 2021 peak, that period sets the top of the scale and any normal market reads well below it. That is deliberate: a sentiment measure rebased to recent conditions would call every quiet market average.

The index measures activity in the primary market, not returns. It says nothing about whether any individual vehicle is worth owning.