The worker sells their labour time in advance of its consumption by the capitalist, even though the worker is paid after their labour-time has been expended (Marx 2024, 147). Although the worker’s labour-power is bought ‘on credit,’ the contract is struck before their labour-power is consumed (Marx 2024, 148). Once the capitalist has bought labour-power, the worker generally has some job security (even if this is only the meagre cost of finding their replacement), which deters the capitalist from terminating the worker immediately after their hire. Each purchase of labour-time is a kind of bet by the capitalist, wagered against the worker’s termination cost. The capitalist speculates that they will be able to extract the entirety of value they’ve paid for (and, especially, the value they haven’t paid for) from the worker (Marx 2024, 205).

In aggregate, the capitalist runs the risk of under-purchasing or over-purchasing labour-time. Both are considered undesirable. If the capitalist under-purchases labour-time, the means of production will be under-utilized, a ‘mere loss’ in the capitalist’s eyes (Marx 2024, 280). If the capitalist over-purchases labour-time, workers will run into a shortage of tools or raw materials (the means of production), and some of the capitalist’s purchased labour-time will be wasted in idleness (Marx 2024, 214). When a capitalist realizes their old projections were inaccurate, course corrections can be devastatingly breakneck. These corrections cause the sawtooth movement of the capitalist boom and bust cycle (Marx 2024, 579). A capitalist’s projections seek the equilibrium between over- and under-purchasing labour-time. The capitalist aims for an infinitesimal target: complete utilization of the means of production, with zero idle labour-time (Marx 2024, 234).

The difficulty of the capitalist’s speculation increases with the duration of purchased labour-time. Projecting the amount of available means of production a single day in advance is relatively easy, but projecting a year in advance is more difficult. Ideally (for the capitalist), the duration of purchased labour-time would tend toward zero (Marx 2024, 512). Absolutely interchangeable workers would sell labour-time by the split-second, and reserve workers would always remain on call. The employer could lay workers off at a moment’s notice, with zero replacement cost. This ‘ideal’ scenario is hyperbolic only if it currently seems technically or legally unfeasible. The capitalist’s profit incentive encourages them to overcome technical or legal barriers to shrinking the duration of purchased labour-time, especially when productivity stalls (Marx 2024, 234).

Marx 2024: Capital Vol. 1, trans. Reitter