This is a very difficult question to answer, because it is hard to measure something like social impact. However, we can say that the book did impact society for several reasons. First, Lord the Flies was considered of the the important books by the American Library Association.
In 2005, the novel was called one of the best novel from 1923-2005 by TIME magazine. And perhaps most importantly of all, it was required reading in many school in America. In light of these points, we can surmise that the book did speak to many people in the English speaking world.
Many people gained a more realistic view of human nature, that is, human nature is dark and self-serving when there are little social constraints. In the least we can say that this understanding has had a hearing through the Lord of the Flies.