The Math of Getting Squeezed — Das Kapital

Marx formalizes how three variables, working-day length, labour intensity, and productivity, determine the split between wages and surplus-value. Assuming a constant twelve-hour day, rising productivity lowers the value of labour-power and raises surplus-value; they move in opposite directions. Changes in surplus-value follow from changes in productivity affecting subsistence goods, not the reverse.

Ricardo's formulas are corrected: proportional shifts depend on the original division of the day. When intensity rises, more value is created in the same clock time, so both wages and surplus can rise while exploitation deepens. When the day lengthens, surplus-value grows absolutely and may also rise relatively if wages lag behind wear and tear.

Legal limits on hours matter because capital otherwise pushes intensity and extension until the worker's reproduction breaks down. The chapter closes with combined cases: dearer food plus longer hours during wartime England, and the possibility that higher productivity with shorter days could free time for human development if capital were abolished. Under capitalism, however, spare time for one class is purchased by converting the masses' lifetime into labour time.