Formula Twins (exact-twin / near-twin)
Our term for a cluster of products sharing an identical formula across multiple brands. An "exact-twin" cluster requires every compound, form, rounded elemental amount, and serving size to match precisely; a "near-twin" cluster relaxes the match to the same compounds and forms and the same serving size, ignoring the declared amounts.
Example
4,192 exact-twin clusters cover 17.0% of on-market products; loosening the match to near-twin raises that to 27.8%.