That happened when the Fed removed the interest rate restrictions on deposits. Used to be a flat 5% in savings. That was it, no deviation. When they removed the cap came the dawn of high interest rate CDs. But what the general public failed to understand was back then there were almost no large National banks. Banks were local and if they paid you 18% for your CD, they had to charge 21% for mortgages because that was how they made the money to pay you!