Mortgages were short-term, usually for three to five years, and they were not amortized. In other words, people paid interest, but did not repay the sum they had borrowed (the principal) until the end of the loan's term, so that they ended up facing a balloon-sized final payment. The average difference (spread) between mortgage rates and high-grade corporate bond yields was about two percentage points during the 1920s, compared with about half a per cent (50 basis points) in the past twenty years.