What is meant by the term shrink or shrinkage?

Consensus is actually very hard to find on what the term ‘shrink’ or ‘shrinkage’ means and what should be included and excluded when it is being calculated. Some authors regard it as a catch all for a wide range of losses suffered by retailers, including both crime-related events such as staff and customer theft, and errors incurred as part of the process of retailing, such as incorrect pricing, changes in price, damaged products and food items going out of date, while others only seem to use it to refer to variance in the value of expected and actual inventory.