Artificial contraceptives are not a hundred percent effective. Each method has its own failure rate. Given the such a failure rate and a starting population size, what is the effect on population growth?
For this quick study, I chose condoms because they're the most popular, because they're not permanent, and they don't have any side effects, barring latex allergies. I ran the numbers through a spreadsheet and came up with surprising results.
Condoms have a typical use failure rate of 14% and a perfect use failure rate of 2%. Perfect use means that they are used correctly each and every time a couple has sex; usually this means laboratory conditions. Typical use means that they are used, but sometimes incorrectly, as happens in real-world conditions.
Given a starting population of 100,000 fertile women, assuming they have sex once a month, assuming no gaps between delivery and subsequent pregnancy (women who have delivered babies are immediately reintroduced into the sexually active population, i.e., after nine months), assuming all pregnancies come to term, and taking a five year period, I came up with the following figures:
This shows that the number of pregnancies per month eventually normalizes at 6,600 somewhere in the middle of the third year. This also shows that in any given population of typical condom users, more than half will eventually be in the pregnant state.
The sum total of children to be born -- given typical condom use -- in this sexually active population of 100,000 women over this five year period is over 400,000. This corresponds to about 4 children per family, or a 200% increase in population.
Total cost of birth control for 100,000 women over the five years,at P10 per condom: about P30-M.
Using the "perfect use" scenario of a 2% failure rate, all other assumptions held constant, the number of pregnancies per month normalizes at 1,700 a little after the end of the first year. This corresponds to 14,000 pregnant women at any given time. Over a five year period, the number of children to be born is 100,000, or a 30% increase in the population.
Total cost of birth control for 100,000 women over the five years, at P10 per condom: about P52-M.
Please review my computations to see if the figures are correct.