Does anyone know how typologically common it is to have number agreement on nouns even when that noun's plurality is implied by numerals?
For instance, in Spanish "two houses" is "dos casas", i.e, the noun "casa" is marked for plural even though we already know there's two of them. Why not "dos casa"?
Are there more languages in which plural marking is always obligatory or more in which plural marking becomes optional with numerals? Is either strategy related to other features?