Why do my shirt collars shrink when commercially laundered?

Question

Before you smirk and say lose some weight, I have shirts purchased around the same time whose collars have not shrunk. Among my shirts, Lands End and Joseph A. Bank dress shirts seem unaffected by laundering while all the rest, even some pricey brands, shrink at the collar within two years. And, why are the collars affected and not the sleeve lengths, which show little or no shrinkage in any of the shirts?

Answer 1

It could be either the thread used or the filling in the collars used!