The play Death of a Salesman, by Arthur Miller, reflects the mentality of the post-World War II generation of Americans who saw, for the first time in decades, the effects of a restored economy which the upper- middle and middle classes were able to enjoy.
The social realism is evident mostly in that Happy, Biff, and Willy represent the strata of society that was not able to enjoy the benefits of achieving what became to be known as the "American Dream." The reason for this is because Arthur Miller cleverly portrayed these men as "all dream, no action." For instance, Happy is a sales clerk, Biff is a farm hand, and Willy is a salesman. None of these occupations benefited from the boom in the economy of the post-war era. Yet, these three had nothing but the American Dream in their heads. That is where the big clash occurs between the Loman's social fantasies versus the social reality of the time. They continue to dream and to create ridiculous "strategies" that could lead them to attain financial freedom and yet they fail in every attempt.
However, there is more depth to this than a mere capitalistic view of reality: Miller wants us to remember the importance of being true to ourselves when approaching our dreams: There is no "quick fix it" to happiness. It is a process of trial and error that needs to be embraced realistically and consistently. Reality and consistency were the exact two elements that the Loman family lacked in tremendous amounts. That is the main reason why their "dreams" never materialized.
While not immediately considered to be a social realist, I think that Miller fits the conditions of the social realism movement quite effectively. This is seen in Willy. The depiction of his protagonist is one where Willy is an example of how not to live one's life. Yet the challenge, as Miller himself noted, is that the conception of the American Dream and its emphasis on materialism compels individuals to not have any choice:
...the central matrix of this play is ... what most people are up against in their lives.... they were seeing themselves, not because Willy is a salesman, but the situation in which he stood and to which he was reacting, and which was reacting against him, was probably the central situation of contemporary civilization. It is that we are struggling with forces that are far greater than we can handle, with no equipment to make anything mean anything.
In Miller's own configuration, modernity has configured a setting where individuals, despite having choice and freedom, do exactly what they do not want to do. In the pursuit of dreams and material realities where there are greater chances of failures than successes and where accompishment is never really recognized, Miller is calling attention to a problem that he believes requires changing. In depicting Willy in the manner he does, Miller is demanding for individuals to visualize the world as it should be as opposed to what it is. In this, I think that a heavy emphasis on social realism is present. Willy dies as "someone," though it is not as he imagines. For the social realist, Willy dies as a symbol of how materialism can ruin lives and any "dream" built upon such a firmament is fragile beyond belief. Miller is calling for this state of affairs to change, and is representative of social realism.