The previous factors that we’ve seen, such as price and volume, book-to-market, and analyst forecasts, tend to occur at regular intervals, whether it’s daily or quarterly. Another class of factors are based on events that may not be scheduled and may have a significant impact on the stock price. For example, when the Deepwater Horizon oil rig exploded in the Gulf of Mexico in 2010, British Petroleum saw its share price drop from $60 to under $30 per share over the next 40 days. In 2016, when Microsoft announced its intention to acquire LinkedIn, the share price of LinkedIn jumped almost 50 percent on that day, while Microsoft shares decreased by three percent. Events can be either macro level events such as natural disasters, major changes in government, or changes in interest rates by central bank. Events can also be corporate events such as mergers and acquisitions, spinoffs, and new product announcements. Still other common events are index ads or index deletions and even weight changes for major indices. Many kinds of events are one-off and rare events, but some, such as earnings releases, earnings guidance, and product announcements, can be expected with some regularity.