I've noticed this slightly diminishing size with all kinds of products, just enough not to stand up
and scream at us, and of course, always at the same old price.
For example, Hellman's Mayo that used to be 850 ml. (whatever that is), now for the same price: 710 ml. Even I am smart enough to know that 710 is less than 850, even though I have no idea what size either of them is.
Tricky Dick.