margin requirement, that part of a security's price that a buyer must pay for in cash. The balance of the price is met by the broker, who, in effect, is supplying a client with a loan. The smaller the margin, the greater the inducement to speculation. Low margin requirements were considered an important cause of the 1929 collapse of the American stock market. In 1934, the Securities Exchange Act gave the Federal Reserve Board the power to regulate margin requirements. The amount has been reset at various times, but in recent years, the Federal Reserve has instituted a 50% margin requirement with a $2,000 minimum.