How do credit ratings work in the USA?

Credit ratings are a numerical value meant to represent the creditworthiness of a person. This is the likeliness that a person will pay their bills. There are many different methods of calculating credit scores, the most prominent of which being the FICO system. FICO used to stand for "Fair Isaac Corporation", and they would be contracted by mortgage lenders to determine the likelihood that their debtor will default on their payments.Most private mortgage insurance companies will not provide insurance for borrowers with scores below 660.