Auxiliary for the same verb after than / as
I earn less than he he earns.
I earn less than he does.
Auxiliary depends on tense
He knows more than I did at his age.
Omitting the verb in formal English
I'm not as cunning as you (are).
He has more time than I/we (have).
I have to work harder than she (does).
I play chess better than he (does).
You can't type as fast as I can.
Omitting the verb in informal English
He has more free time than me.
They are much richer than us.
They work harder than us.
You can't type as fast as me.