Global fertility rate has been declining significantly since 1965 to today. Although this is negative for government taxation revenue and the economy, an argument can be made that falls in global fertility rate is good for lowering congestion and traffic, reducing pollution, and reducing animal suffering.

Regardless, if prostitution is legal, do you think this would increase or decrease the fertility rate?

One argument can be made that if sex work is legalised, many men will stop dating or marrying and will simply visit prostitutes all the time, which means men no longer marry or have children. This is similar to the argument against sex bots, which claims that if sex bots were legalised, men will simply have sex with sex bots and won't fulfil the social expectation to date, marry and have children with women. This would in effect lower the fertility rate.

Another argument can be made that if sex work is legal, many women will become prostitutes. This pushes the price of sex down as there is increased supply. Lower price of sex means that many men may find that it is cheaper to pay for sex at a brothel compared to marrying and dating.

Legalising sex work may also mean that there is a spike in demand from men who visit sex workers, leading to an increase in prices. Suddenly many sex workers are earning huge amounts of money. Women who give away sex for free while dating or marrying may hear about the huge sums or money their sex worker colleagues are making and feel there is a huge opportunity cost to dating and marrying, which compels them to also enter sex work rather than look after a baby.

However, any argument can be made that there are many men who simply want sex and do not want children. If prostitution is legal, these men have sex with prostitutes and do not need to enter the dating and marriage market to get sex. However, if prostitution is illegal, then these men who only want sex without any commitment will be forced to enter the dating and marriage market and try to get sex with as little commitment as possible. What this does is that it creates a situation where women who want children are unable to distinguish between those men who only want sex and those who are willing to commit to having children. This leads to many women feeling used if they have sex with a man who turns out to only want sex, and many women may simply exit the dating and marriage market as a result. Basically because the dating and marriage market is tainted or polluted with men who want commitment-free sex, it takes a long time for women to finally find the right man, and once she does she is likely to be older, which means she will have fewer children as her fertile years are limited.