uniting labour power with the means of production. From that point on, Marx argues, labour power at work is transformed into capital, specifically variable capital which accomplishes the valorisation process. Functioning as variable capital, living labour creates both use values and new value, conserves the value of constant capital assets, and transfers part of the value of materials and equipment used to the new products. The result aimed for is the valorisation of invested capital, i.e. other things being equal, the value of capital is maintained and has also increased through the activity of living labour. At the end of the working day, labour power has been more or less consumed, and must be restored through rest, eating and drinking, and recreation. Medical estimates of the average holiday time necessary for fulltime workers to fully recuperate in a physiological and psychological sense from work stress during the year differ from country to country; but as an approximate gauge, three weeks continuous holiday is physiologically optimal for the average worker. ILO statistics show a wide range of average hours worked and average holidays for different countries; for example, Korean workers work the most hours per year, and Americans have fewer formal holidays than West Europeans. Several researchers have questioned however to what extent additional hours worked really increase the marginal productivity of labour; particularly in services, the work that gets done in five days could often also be done in four. The most difficult aspect to measure is the intensity of work, though some argue the incidence of work accidents are a reliable yardstick. If workers are laid off by an organization, but the organization continues to produce the same amount of output or services as before, or even more, with the same technology, we can often conclude that the intensity of work must have increased. Reproduction Marx himself argued that: This understanding, however, only captures the sense in which the reproduction of labour power comes at no cost to capitalists, like the reproduction of ecological conditions, but unlike the reproduction of, say, machine bolts and plastic wrap. Elites and governments have always sought to actively intervene or mediate in the process of the reproduction of labour power, through family legislation, laws regulating sexual conduct, medical provisions, education policies, and housing policies. Such interventions always carry an economic cost, but that cost can be socialized or forced upon workers themselves, especially