Hi.

In my previous message, the proof is wrong because of a typo... it should 
go like this:

Proof.

For the average we need the amount of subclasses, and on the other hand the 
amount of classes. But each is one of the others except nil's subclasses. 
There's only one of those (Object), then the average of subclasses per class is

(amountOfSubclasses) / amountOfClasses =
(amountOfClasses + 1) /. amountOfClasses =
1 / amountOfClasses + 1,

that is, arbitrarily close to 1 as the amount of classes increase.

Andres.