There are a bunch of manga magazines like:
There is a different of the total amount of page for every series that published in each of manga magazine in japan every week/month. The total amount of page for weekly serialization, has about 18-20 pages for a one chapter each week. For a monthly magazine, they have around 30-50 pages each month.
According that, what started this format to be a common in a manga industry? I mean, since when this a mount of page for weekly/monthly manga magazine used ?
Additional info : There is already a question that similar with this kind of topic, but it didn't answer my question
Related Topic : What was the first manga magazine?