Krugman’s way of thinking could apply equally well to acts of crime. Suppose I steal $10,000 from you. My wealth goes up. Your wealth goes down. But the wealth of society as a whole hasn’t changed at all. Right? Wrong.
Remember the original Jamestown colony? In 1607, it started out as an experiment in socialism. “We” really did own everything collectively and “we” nearly starved to death. But then a new governor substituted “mine” and “thine” for “we” and the colony began to prosper. Who owns what and why and the ability to be secure in what we own is hugely important for growth and prosperity.