What is the economic value of a human life?

If there are multiple methods to use in calculating, what are they, which method is preferred, and why?

Considerations/sub-questions on methods

A. Is the calculation purely based on output value (i.e. wages, goods produced, etc.), or are there intangibles that must be included (value of innovations that cause progress for society, NPV of progeny, etc.)?

B. As a result of #1, are there things which reduce economic value in one's life? For example, when one has gone on unemployment, is one's net economic value negative for that period of time?

C. Is the economic value of life dependent on one's country/state/locale or the sector one performs in? For example, is it correct to say the economic value of a life is different in the US than in South Africa (due to average output in real terms?