Standard & Poor's

Standard & Poor's (S&P) is one of the three big credit rating agencies, alongside Moody's and Fitch. It grades how likely governments and companies are to repay their debts, from AAA at the top down to D for default. A downgrade can raise a country's borrowing costs and weigh on its currency.

Its sister business, S&P Dow Jones Indices, runs famous benchmarks like the S&P 500. In 2011, S&P made headlines by stripping the US of its top AAA rating for the first time.