For several years I have advocated the use of Final Sales of Domestic Product to measure money expenditures. This is as opposed to GDP. (Scott Sumner is always calling it NGDP, which is a bit redundant. RGDP is GDP corrected for changes in the price level.) The difference between the two measures is changes in inventories. Perhaps remembering early explanations of Keynesian economics, where unplanned inventory investment plays a key role in keeping expenditure equal to output, it was just those changes in inventories that I thought should not be included in a proper measure of monetary expenditure. Counting goods produced and not sold as having been purchased by the producer hardly counts.
While I still think that intuition is correct, it is based upon identifying inventories with stocks of unsold final goods. Cars are sitting on the lot or cans of beans are sitting on the shelf in the grocery store. What of other types of inventories? I am especially concerned with partially finished goods.
Perhaps keeping the focus on the future--the target should be for Final Sales for Domestic Product in a year, makes it so that every part of inventory changes can be ignored. However, more study is needed and I am more and more thinking that the best measure doesn't yet exist.