Prerequisites:

Description:

    This is the technology of advancing the lifespan of members of the populace dramatically.  Exactly how much extension is possible and how difficult it is to achieve will depend on the rules of the universe in question.  The degree of extension possible in the real universe is thoroughly unknown, but certainly nonzero.  The amount of cost associated with each person's life extension will also vary.  It may be that the cost associated with keeping a single person alive indefinitely may be more than the work actually generated by an average person.  In that case, only a small subset of the whole population may have extended lives.
    One effect this extension will have is to reduce the attrition rate on training and education.  Ordinarily, money spent on education will be lost after the members of the generation it was spent on have died.  With longevity extension active, this need not be the case.
    Another effect is on morale and time perspective.  As an example, the most of people of ~2000 Earth didn't feel very affected by the imminent running out of petroleum.  This is because many of these people felt that the problem would happen after their own deaths.  If these people had had a life expectancy of 200 years, however, this problem probably would have been dealt with before having such large economic impact.  Similarly, people who have long life expectancies will not become as disheartened by short-term problems.  How young people feel for this time will also affect how much morale is altered by this technology.  Living a thousand years and feeling like you're 90 the whole time would not be as nice as living a thousand years feeling like you're 20.
    The third big effect of this technology is the most obvious: people don't die as often.  This means that the population growth rate, instead of being the birth rate minus the death rate, will instead approach a state of being simply the birth rate.  This could easily lead to overpopulation.  Of course, accidents and emigration will still cause populations to decrease, and the social/economic situation might require some people to die of old age anyway, so some death will still happen.  Other measures, such as forcing people to wait before having children, or only allowing certain people to have children, etc. may be needed to keep the population in check.

    The development of this technology will affect: (1)  the total amount of life extension possible (lifespan), (2) the effective age of people under the treatment (biological age; how old they look/feel), which strongly affects the morale aspect, (3) the economic cost of keeping someone alive/young.  The ratio of these effects and the total possible effect of each will vary from universe to universe.