There are stereotypes, but you can't really judge any particular person by his given name.
You might expect "Billy Jeff" to be a mechanic and "Winston" to be a banker, but you could be wrong as well.
America is a land of aspiration and I have seen a study that showed that names that are popular ripple down through the social classes. When a name is popular among the upper classes, those in the lower classes start to adopt the name (because they think it sounds classy or sophisticated).
Of course, like all things trendy, once it becomes too common, the upper classes move on to a new set of names.
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