Might or might have had

'The population of the area was at its highest about 150 years ago, when a typical village might have 500 inhabitants, whereas now some villages have as few as 100 permanent inhabitants. '

I know that 'might' can be used to refer to the present or future or past in reported speech, but the passage here uses 'might' and not 'might have had' although the reference is to the past.Could you explain, please?

Thanks