The issue of perishability also means that events venue managers may have to use a variety of techniques, such as differential pricing, to try to encourage activities in quiet periods when a facility or service on offer might not sell. Perhaps a mobile disco can be obtained at discount for an event on, say, a Tuesday, rather than at a peak period the week or year, like a Friday or Saturday night or New Year's Eve. This too illustrates the perishability issue; if the disco is not booked one night of the week it will have lost that night's revenue forever.