=== Unemployment rate === Labour, an important economic factor for any person in the world, is not only a means of income but also a sociobiological drive. That is, labour is also a way of fulfilling primal and evolutionary needs. It’s a wild desire, deep within us, to give things value and to split tasks among our peers. The unemployment rate is a well-known economic indicator that, first and foremost, depends on the dynamics of the economic agents in a country. However, the “working instinct” of these economic agents depends on the sociobiological dynamics cited earlier. Therefore, there are two dynamics, two systems fused into one single indicator: one of them, the “economic”, made-by-men one and the other, “sociobiological”, made-by-nature one. It is therefore an unusual indicator that binds a known endogenous system and a known exogenous system together. Digging closely into the indicator now, we can say that the unemployment rate tends to zero in a booming Keynesian economy that reached the plateau of having equal amounts of savings and of investments for a given equal levels of aggregate prices and of aggregate wages, compared to a previous, non-zero unemployment rate time-lapse far from the equilibrium. Moreover, it also tends to zero in a society under sociobiological drive because all individuals are able and ultimately want to divide labour. Hence, we can say that the unemployment rate is a covariant indicator between those two systems because it tends to the same value - zero - when the efficiencies of the systems which are being measured tend to the maximum.