The city jail budget has soared to an all-time high even as the number of inmates has dropped to the lowest point in three decades, according to a new analysis by City Controller Scott Stringer.

The city shelled out $1.36 billion to run Rikers Island and its other jails in the 2017 fiscal year a 44% jump since 2007.

Costs skyrocketed despite the prisoner population dropping to the lowest point in 34 years, an average of 9,500 a day.

“We need a smart, modern, and fair corrections system. Right now, the inmate population is at its lowest point in decades, but costs continue to rise dramatically. An extraordinary decline in inmates should yield cost-savings and better all-around outcomes not dramatic spending increases. That’s what’s so alarming about the numbers,” Stringer said.

Scott Stringer backs closing Rikers faster than de Blasio’s plan

It now costs the city a whopping $143,130 a year to keep each detainee in jail up 112% over the last decade.

When other costs that aren’t part of the Department of Correction budget, like medical services, pensions and fringe benefits, are included, the cost jumps to $270,876. That adds up to $742 per inmate per day.

Even though DOC employs 10,862 uniformed correction officers more than the number of inmates overtime payments have remained high.

The city spent an average of $28,045 in overtime for every inmate in 2017.

Jail workers should get on the Rikers closure bandwagon

“We have to do better,” Stringer said. “We’re putting far more money into far fewer inmates. It’s one of the many reasons that I believe we need to close Rikers on a quick timeline and take a 21st century approach to criminal justice.”

Mayor de Blasio has pledged to close Rikers in a decade, while Stringer says it can be done faster.

All the spending has not added up to safer jails, Stringer found.

There were 1,332 fight and assault infractions per the 1,000 average daily population in 2017, up 16% from the year before.

The rate of inmate assaults on staff went up 6%, while use of force by correction officers fell 1%.

“We’re proud of our success in reducing the jail population, and we’re proud of the reforms that have made Rikers safer for staff and inmates. Our investments in safety and skills development for staff and inmates cost money but have been key in improving conditions in our jails,” said de Blasio spokeswoman Natalie Grybauskas.