Some say we have been in a bull market since 1982. This happened in Japan in the 1980s, when, due to a real estate market crash, the value their assets that showed up on their books was not really worth that much. When things evened out, the Tokyo stock market fell from 40,000 to 13,000. This avoids investors of having to deal with currency conversions. By lowering interest rates, they increase the likelihood companies will borrow and use this capital to grow their business.
Growth is best if slow and controlled.
This allows potential buyers to compare its returns to that of other investment vehicles, such as bonds. What is leftover is the equity. This, however, is not always easy to determine, because assets show up the financial records at their purchase price. This is why so much emphasis is placed on a comapny's earnings announcements, but this is also why buying stocks is so complicated. Estimating earnings next year is a formidable task in itself, but estimating them 10 years down the road is next to impossible.