Usually, average utilitarians are interested in maximizing the average well-being of all the people that ever exist, they are not fundamentally interested in the average well-being of the people alive at particular points of time. Since some people have already existed, this is only a technical problem for average utilitarianism (and a problem that could not even possibly affect anyone’s decision).
Incidentally, not distinguishing between averages over all the people that ever exist and all the people that exist at some time leads some people to wrongly conclude that average utilitarianism favors killing off people who are happy, but less happy than average.
A related commonly missed distinction is between maximizing welfare divided by lives, versus maximizing welfare divided by life-years. The second is more prone to endorsing euthanasia hypotheticals.
Usually, average utilitarians are interested in maximizing the average well-being of all the people that ever exist, they are not fundamentally interested in the average well-being of the people alive at particular points of time. Since some people have already existed, this is only a technical problem for average utilitarianism (and a problem that could not even possibly affect anyone’s decision).
Incidentally, not distinguishing between averages over all the people that ever exist and all the people that exist at some time leads some people to wrongly conclude that average utilitarianism favors killing off people who are happy, but less happy than average.
A related commonly missed distinction is between maximizing welfare divided by lives, versus maximizing welfare divided by life-years. The second is more prone to endorsing euthanasia hypotheticals.