In the XXXX's VS In the XXXXs
In the XXXX's VS In the XXXXs

Could you tell me which of those two is more common? For example, "In the 1980's" VS "In the 1980s" Thank you!

Question

In the XXXX's VS In the XXXXs
In the XXXX's VS In the XXXXs

Could you tell me which of those two is more common? For example, "In the 1980's" VS "In the 1980s" Thank you!

Answer

the 1980s ( Eighties ) without the apostrophe is more commonly used.
The use of  the apostrophe is declining and not necessary !

Answer

You say a, one, two, several, etc. hundred without a final ‘s’ on ‘hundred’. Hundreds (of…) can be used if there is no number or quantity before it. Always use a plural verb with hundred or hundreds, except when an amount of money is mentioned: Four hundred (people) are expected to attend.Two hundred (pounds) was withdrawn from the account.

the… hundreds [plural] the years of a particular century 
the early nineteen hundreds (= written ‘early 1900s’)