The City Budget usually sets the number of line officers, and supervisors needed to safely run a shift. Depending on the size of the precinct and it's needs, the numbers can differ. When there are vacancies on a shift, people may have to double up on the area they patrol, or they have to hire overtime.
In New York State Corrections where I worked under Mario Cuomo, there were times when there was zero overtime allowed to save the State money. If an officer called in sick, they'd shut that job down for the day, or an officer with his own unit to watch, was made to watch two units for the shift. As a messhall Sergeant, there were plenty of times I was the only Sergeant in the prison covering the breakfast chow run with 1200 inmates to feed, and a handful of officers to keep peace in the messhall.
I lived in the 77 in the 1970s. “No Radio” and Son of Sam.
God bless the NYPD.
On a related point, ION Television network took “Blue Bloods” off their schedule with no explanation. It made my Wednesdays under lockdown bearable. I hope it’s not because they hate cops or anything.
The gritty and intense “Chicago P.D.” is still on however. I wonder how long before BLM etc object to that program.