Our growing prison population is mostly due to one thing, our failed War on Drugs(tm).
That is only part of the reason.
We are now going toward sex base "crimes" to begin to help full up our jails.
There is for example nonsense going around that hundreds of thousands of young people mainly girls are being force into the sex trade every year in the US.
A study was done where it was claims that kind of large numbers of teenagers was at risk
of being part of the sex trade and they included every teens living within a short distance of the Mexican border for example.
When the news media got done with this study it was no longer an at risk claim but those was the numbers being reported as taking part in the sex trade.
As a result in order to fight this almost non-existed trade new laws are being pass to give young teens hookers a free pass for hooking if they can point to someone who force them into the trade with decades of prison time for the person they charge with forcing them into hooking.
Then they added that if a john picked up a hooker and she turn out to be 16 years old then away the john go for a minimum of 5 years.
Then we have crazy child porn laws where if a teenage male have a naked picture of his under 18 years old girlfriend off to prison he goes for four years minimum even if they are living in a state where the age of consent is such that legally they could have sex every night of the week. He just can not have a picture of her even if he can screw her all he wish to.
One way or another with special note of the private prisons now coming into being we will find ways and reasons even with a dropping crime rate to keep our prisons full.