Joseph Kennedy, Sr., sold the stocks he owned before the 1929 stock market crash and made millions based on some stock tips from a shoeshine boy. Kennedy figured if the market was popular enough for a shoeshine boy to talk about it, the speculative bubble was too big and about to burst. In the years to follow, some of the many repercussions of the crash would be the failure of thousands of banks and the loss of employment for nearly one-fourth of the workforce (before the days of unemployment checks); it is estimated that millions lost their life savings in the stock market crash of 1929. The main cause of the market crash was the excessive "buying on margin" done by so many speculators. This was a system by which a buyer of a stock only paid for 10% of its value initially, and by the time the remaining balance was due to the broker, the value of the stock had risen by that much or more, so the buyer could then sell it back, pay off the broker what was owed, and pocket the difference.