Payload ratio XML, JSON?

Question

JSON

Is there such a thing as an XML payload ratio or something like that.
What do I mean by this concept: since XML or JSON before parsing (during transmission) is still a string in which there are attributes and their values, the efficiency is something like the ratio of the length (size in bytes) of the lines of this same data to the length / the size of the entire document/line.
Just from the exchange files of some "mega fancy" CMS, the eyes begin to bleed in terms of this efficiency.

Answer 1

It all depends on who organizes this data and how. Since the developer invents the names of the Json / xml attributes himself, then the proportions here can be of a completely different scale. These formats were created to be able to work with them, unlike any dbf, etc.
In addition, you can "take" and pack XML, as Microsoft did with the docx and xlsx formats. (This is off topic)
With regard to proportions, such a concept as url-encode is more understandable - converting binary data to ascii. There is an obvious increase in the volume of percent from 30 or more. Such a comparison with JSON/XML is not very suitable.