Self sustainability

Formal definition

1. Let E be a random variable that denotes the steady state number of external entities on which the system depends. Let p ( v ) be the probability that the system depends on v external entities, p ( v ) = P ( E = v ) . Then, the system self-sustainability, S , is S = p ( 0 ) .
2. Let e t be the expected time during which the system is self-sustaining from time 0 up to time t . Then, the system self-sustainability is the steady state fraction of time in which it is self-sustaining, S = lim t → ∞ e t / t

Political states

Autarky exists whenever an entity can survive or continue its activities without external assistance. Autarky is not necessarily economic. For example, a military autarky would be a state that could defend itself without help from another country.

Labor

According to the Department of Labor of the state of Idaho, an employed adult shall be considered self-sufficient if the family income exceeds 200% of the Office of Management and Budget poverty income level guidelines.

Peer-to-peer swarming

In peer-to-peer swarming systems, a swarm is self-sustaining if all the blocks of its files are available among peers (excluding seeds and publishers).

Self-sustainability and survivability

Whereas self-sustainability is a quality of one’s independence, survivability applies to the future maintainability of one’s self-sustainability and indeed one’s existence. Many believe that more self-sustainability guarantees a higher degree of survivability. But just as many oppose this, arguing that it is not self-sustainability that is essential for survivability, but on the contrary specialization and thus dependence.

Consider the first two examples presented above. Among countries, commercial treats are as important as self-sustainability. An autarky is usually inefficient. Among people, social ties have been shown to be correlated to happiness and success as much as self-sustainability.