Fair point - the population numbers are largely due to the (most common) marital structure, and societal expectations around having kids.
The amount of sex though definitely includes hookups and a lot of sex outside of the acknowledged marital structure. A large number of those kids may well be illegitimate, I suspect no one wants to look too hard.
I also suspect what is happening in the US is a combination of defacto ‘strikes’ from both sides of the equation, combined with general confusion as to what to do or why. Essentially a ‘why would I want to engage with this mess? What’s even in it for me?’.
I suspect that for all the attention certain politics and niche subcultures promoting disengagement get, it mostly comes down to spending less time in mingly social environments with the opposite sex, something young unmarried Indian men frequently expressed disappointment with and is also increasingly the case in the West for a different balance of reasons. The average reason may be different, but of course the US has its small towns full of conservative parents and India has its internet addicts and workaholics.
(Not sure if there are directly comparable surveys, but I wouldn't be surprised to discover that unmarried Americans were rather more sexually active than unmarried Indians, even with the downward trend)
The amount of sex though definitely includes hookups and a lot of sex outside of the acknowledged marital structure. A large number of those kids may well be illegitimate, I suspect no one wants to look too hard.
I also suspect what is happening in the US is a combination of defacto ‘strikes’ from both sides of the equation, combined with general confusion as to what to do or why. Essentially a ‘why would I want to engage with this mess? What’s even in it for me?’.