What is the difference between how the poor are put to rest in the graveyard versus how the rich are put to rest within the graveyard?

Rich people are buried in the earth of the graveyard within their own plots with gravestones above. Poor people, on the other hand, are stacked one on top of another within concrete boxes in the graveyard. Even in death, the disparity between poor and rich in the novel's society is underscored by the author in order to support his intended messages.