A sub prime mortgage is a mortgage granted to a person whose credit is below (sub) the preferred (prime) level acceptable to standard lenders. Deregulation on Wall Street combined with rampant greed to encourage those with below-par incomes and credit scores to apply for loans for houses they could not afford. During the early twenty-naughts, hundreds of thousands of Americans found themselves with house payments equal to 50% of their take-home pay, far above the 25% of thirty years ago. When interest rates increased, these people were left paying upwards of 75% of their income on house payments. Inevitably, these people defaulted on their mortgages, greatly contributing to the recession which started in the fall of 2008.