Pat Gunning refers to the "distinction between productive and unproductive labor." The Physiocrats and Adam Smith certainly emphasized this distinction. To the extent that it was meant to distinguish the production of wealth from the provision of services, I believe it is an important distinction.

It is unfortunate that the neo-classicals & others have forsaken a precise & functional definition of the term wealth. Of course, lumping goods & services together makes the aggregates more amenable to statistical treatment. However, tracing the laws governing the production & distribution of wealth thus becomes more difficult. Adam Smith in the W of N repeatedly referred to the real wealth as the annual produce of the land & labour of a society.

Roy Davidson