Dear AZ:

You wrote:
> A)A hundred people left our town this year, the most for seven years.
>
> Could this mean that this is the highest number of people that will leave
> our town in a singal year in a period of time starting this year? Could it
> refer to any period of time other than the last seven years?
>
> B)A hundred people left our town this year, the majority for seven years.
>
> What does this mean? That the majority of the hundred people left for a
> period of seven years and will come back after seven years?
>
Neither of these sentences are particularly clear because of the placement of the modifier. Sentence B is more understandable because A has the additional problem of an unclear antecedent for “most.” Also “for seven years” means that they would not return until seven years have passed. I think you meant “in seven years,” that is, this is the most people who have left town since before seven years ago.

I would avoid A completely. B means “the majority of the people left for seven years.” It does not say anything about their return and nothing is implied.