The essay aims to draw attention to the view that the adjustment of productive capacity to expected demand implies a qualitative change in productive capacity, which is transformed by the producers with a view to acquiring the means of production, skills and organization necessary to produce new and existing goods and services in a new way. In particular, the essay focuses on the possible long-term effects arising from feedbacks of this transformation of productive capacity, on employment growth, consumption, production and income. In this theoretical perspective, investments are considered as a long-term autonomous component of demand. A system of relationships between investment, consumption and employment is estimated for the United States and Italy over the period 1960-2013. The results suggest that in our contemporary economies decelerative forces are at work. These forces can essentially be attributed to the reduction in the use of labour per unit of production and to the effects of such a reduction on income and employment growth.