As the other attorney indicated, there is no set number that is typical. Since it is very easy to file a charge, there is nothing in itself unusual about four charges. I don't know why one person would file four charges at one time, and doubt the EEOC would accept four. If someone filed four different charges over time, my guess is that the person does not have any valid claims but is desperate. If four individuals filed charges separately, that could be a sign of something, or it could be an attempted coordinated shakedown. Of course, I'm just speculating here.
My real question is how do you know that four charges were filed? Charges are confidential, and the employer probably doesn't even have notice of them yet if they were filed last week.
If anyone is looking for a lawyer at that company, they should contact an experienced employment lawyer. many of us, myself included, will provide a free consultation.
Typically, the employer has 40 days to submit a position statement in response to the charge, unless the parties agree to mediation.
Hope this answers your questions.
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