Fuller used data gathered by the US, German and Swiss armies to arrive at an estimate for the average amount of (mechanical) work a person could do in a year. This is in addition to the energy spent in metabolic self-maintenance. The net work done constitutes a net "advantage" in dealing with the environment. A figure of 37.5 million foot-pounds was arrived at.
We can calculate the ratio of work done by a system to the energy intake, to obtain a measure of efficiency. Since most of our machines and appliances are very inefficient, Fuller posited a figure of 4% overall efficiency for total energy consumption.
He calculated world energy consumption for the year 1950 as being 80.17 quintillion foot-pounds (plus or minus 10%). Given only 4% efficiency the net work obtained equalled 3.2 quintillion ft-lbs. We divide this figure by the net annual energy output per man of 37.2 million ft-lbs. This gives a result of 85.5 billion man-year equivalents done by machines. These man-year equivalents are energy slaves.
If we divide the number of energy slaves by the world population total of 2.25 billion (for 1950) we get a figure of 38 energy slaves per person.
Boyden (p.196) reports that,
"In the USA, the daily use per capita of energy is around 1000 MJ; that is, each person has the equivalent of 100 energy slaves working 24 hours a day for him or for her.... In some developing countries, the rate of energy use is less than the equivalent of one energy slave per person."
Fuller plotted the geographical concentrations of energy slaves on his World Energy Map.
Ivan Illich (1974) argued that it would be unwise to believe that human well-being depends on the number of energy slaves at our disposal.
See also Mechanical Advantage.
© Paul Taylor 2001