Very interesting, Linda...AHAH  indeed.

Most ABMs come in two forms - whey-dominant and casein-dominant, whch are
usually marketed as a stage one and a stage two (here in the UK, anyway)
and the usual pattern among formula-feeding mothers is to start off with
stage one and then move on (when the baby starts to fuss and grumble) at
about six weeks or so to the stage two. This is also advised by HPs.

Stage one is whey-dominant in most brands;  stage two is casein-dominant,
and stage two is marketed as taking longer to digest, so it is more
'suitable' (Ha!) for 'hungrier' babies.

This is a sad and doomed-to-fail attempt, now I see it, to mirror the
change in breast milk - which never becomes actually casein-dominant,
however, according to the figures LInda has found.

There was a local study, BTW, which may have counterparts in larger
studies, that showed the proportion of mothers changing from one form of
ABM to another was very similar to the proportion of mothers changing from
breast milk to an ABM - and the most common reason for the change from one
ABM to another was 'the milk wasn't satisfying the baby' , which has more
than a faint echo of 'not enough milk'.

Heather Welford Neil
NCT bfc Newcastle upon Tyne UK