Assume you're considering opening up a store to sell auto racing collectibles. The auto racing industry provides a good example about making assumptions. It experienced dramatic growth in broadcast viewers and race attendance for a number of years beginning in the 1990s. Expecting a 10 percent annual growth in the audience was pretty reasonable, at least for a while.
The economic slump of the early 2000s made that growth assumption unreasonable for almost a decade. However, sponsors are returning to auto racing as a marketing tool because it is still an effective medium for reaching a targeted audience.