Quote Originally Posted by Mechalich View Post
Suicide is actually a distressingly common cause of death (there are a number of countries in the modern world with 2% or more of all deaths attributable to suicide) and while historical data is somewhat hard to come by, it may have been even more common in pre-industrial societies. If even 50% of the suicidal choose sacrifice as their method, that could easily be 1% of the total population.
You also need to factor in the average age of death of the population. If the life expectancy of the population is 50 years (to keep the math simple) then we'll estimate that about 2% of the population dies annually. If the rate of death by suicide is 2%, then we're talking .04% the population dying by suicide every year, way less than the 1% other people have mentioned.

In order to make the logistics work, you could set a Logan's Run type society where it's socially expected that you'll "give yourself to the god" at a certain age (presumably old enough to have finished raising your children).