One of its members was Thomas Jefferson, a lawyer from Virginia. He had been a leader in Virginia, and Virginia had elected him to the Continental Congress. The others on the committee were too busy with the revolution to work on the declaration, so Jefferson wrote it alone. He finished the document in a week.
The time frame is in weeks, so it shows the average bull market cycle is 155 weeks or about 39 months. The average bear market is about 17 months, which actually matches the most recent bear market from October 2007 to March 2009 (17 months). A full market cycle is 56 months.
Bear markets are periods of declining stock market prices that are measured in months or years. Crashes are often associated with bear markets, however, they do not necessarily go hand in hand. The crash of 1987, for example, did not lead to a bear market.