The groups of people that occupy different ranks or levels in society are called 'social classes'. 'Pyramids' resembled the class structures, with the 'largest' number at the bottom.
Explanation:
Society consists of people holding different ranks and belonging to different levels. The ones that hold equal ranks or are equally dignified share a common class. These classes are often arranged in a hierarchy of highest to lowest on the basis of the significance of the classes.
The highest class generally has the lowest population. The population goes on increasing as the class lowers. Apparently so, the class structure appears to be like a 'pyramid'.
