Richard D. Wolff

This may be a naive question, and I apologize if the issue has been dealt with elsewhere, but I am reading Marx's Capital, and I am struck by his claim that the tendency of the profit rate is to fall. Reading some other sources, I see that this is still hotly disputed and that the empirical data don't necessarily back Marx's view. My question is: Did Marx consider ALL wages to count as variable capital, or only the wages of productive laborers who actually add value to a product? Because if he considered non-productive wages to be rather part of the circulating component of constant capital, then the displacement of living labor through mechanization would be offset by the reduction in wages laid out for non-productive labor, and the changes to the composition of capital brought about by mechanization would be far smaller than they would appear if we count all wages as variable capital. Not to mention the fact that the word "profit" is applied to appropriation of value from quite different sources, such as capital gains, ground rent, merchant gains from the differential between discounted and retail commodity prices, and of course the employment of value-adding labor power. I would think lumping all those different types of "profit" together isn't what Marx was doing. Is that right?