# Self-sustainability

A system is self-sustaining (or self-sufficient) if it can maintain itself by independent effort. The system self-sustainability is:

1. the degree at which the system can sustain itself without external support
2. the fraction of time in which the system is self-sustaining

Self-sustainability is considered one of the "ilities" and is closely related to sustainability and availability. In the Economics literature, a system that has the quality of being self-sustaining is also referred to as an autarky.

## 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, $S=\lim_{t \rightarrow \infty} {e_t}/{t}$

## Examples

### 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.[1]

### 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).[2]

## Discussion

### 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.[3]

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.[4]

Self sustainability is closely related to living off the grid. Living off the grid providing vegetables, meats, milks, fruits from the land. living with in your means making your own soap harvesting your own honey, maple syrup, oils,foraging for edible herbs, nuts, flowers. Self sustainability allows one to be independent and not have to make frequent trips to the store.

## Notes and references

1. ^ IDAHO Department of Labor (1999). "Definition of Self-sufficiency." Retrieved on 2010-06-26.
2. ^ Menasche, Rocha, de Souza e Silva, Leao, Towsley, Venkataramani (2010). "Estimating self-sustainability in peer-to-peer swarming systems" Retrieved on 2010-06-26.
3. ^ What and Who is Self-Sufficient? by Katrien Vander Straeten
4. ^