What is the name of the company that conducts exit polling for the major news outlets?

Please read the following article (see link below) on the accuracy of exit polls in 2016 vs. actual vote.  Concentrate only on the section regarding the major reasons exit polls are not as accurate as they are publicized to be.  What factors does the article cite on why the exit polls were not accurate?

What is the name of the company that conducts exit polling for the major news outlets?

Length: not to exceed 500 (enough to succinctly answer the question) 

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