The Cabibbo Ledger: A Factor Census of the First-Row CKM Deficit, Graded Against the Coherent Floor of Its Own Inputs

The first row of the CKM matrix should sum to one. With the Particle Data Group's current inputs it sums to 0.9983(6)(4), a deficit Δ_CKM = −0.0017 ± 0.0007 (PDG review of V_ud, V_us and CKM unitarity, revised August 2025). The deficit has a name in the literature, the Cabibbo angle anomaly, and a significance that moves with the input set: about 2σ on the PDG headline inputs, 3σ if nuclear-structure uncertainties are set aside, near 4σ on the tau-decay value of |V_us|, and near zero on the neutron-decay value of |V_ud|. This paper spends one discipline on that row. The discipline is the factor census with a noise floor, first run at home on a residue of my own program: close the set of explanation classes in advance, give each class its producing test and its price, then grade the claimed factor against the coherent floor of its own inputs before any class is allowed to claim it. I work inside a wider program I call the Theory of Everything; this paper spends none of that program's claims, and its home headline is not spent here. The census holds thirteen classes, seven on the input side and six on the new-physics side. Three input classes and three new-physics classes survive the floor. Five classes die, two of them only as sole movers. No class closes the row inside its own stated errors: a single input would have to move 2.7 of its own standard deviations in |V_ud|, or 4.5 in |V_us|, to do the whole job alone. And the floor itself is wide. The spread of the row across legitimate input sets is 0.0030, wider than the deficit it is asked to explain, and the anomaly has been quoted in at least nine forms that share inputs. The graded size of the deficit, printed at full size in §5, is Δ_CKM = −0.0017 ± 0.0007 on the PDG inputs as printed, about 2σ after the inputs' own scale factors are honored, and between 1.4σ and 2.4σ once the nine quoted forms are counted as looks. That is a ledger that does not close. It is not yet a discovery, and this paper claims neither a solution nor new physics.