I believe shrinkage is most commonly used by retailers to mean theft by employees. Shoplifting is customer theft.

Wow yeah I was really confused. English is my third language and I can often figure words that I don't know from the context except that in this case I interpreted 'shrinkage' as some kind of a tendency do produce smaller products (electronics get smaller for instance). And I thought ok it seems a large package makes the product more visible on the shelves. Then I thought "ok" actually a large package would be hard to sneak under one's shirt. So it would be good for that as well.

At first I thought it mean preventing packages from breaking when they are piled one on top of another for storage. To preserve fragile products inside.

I read the original comment and (before scrolling down) was tempted to chime in that 'in this context, shrinkage means "theft"' before realizing the discussion had already been had.

I could very easily see someone as having read that as physically shrinking in size, perhaps due to compression by repeated handling, as would happen in a store, or heat or other uhhh... harsh environmental factors commonly found in retail establishments. (Sorry, I couldn't think of a second good excuse)