An economy in this stage has a limited production function which barely attains the minimum level of potential output. This does not entirely mean that the economy's production level is static. The output level can still be increased, as there was often a surplus of uncultivated land which can be used for increasing agricultural production. Modern science and technology has yet to be introduced. As a result, these pre-Newtonian societies, unaware of the possibilities to manipulate the external world, rely heavily on manual labor and self-sufficiency to survive. States and individuals utilize irrigation systems in many instances, but most farming is still purely for subsistence. There have been technological innovations, but only on ad hoc basis. All of that this can result in increases in output, but never beyond an upper limit which cannot be crossed. Trade is predominantly regional and local, largely done through barter, and the monetary system is not well developed. Investment's share never exceeds 5% of total economic production. Countries in this stage could include Ghana and Togo.