Whether leftists know it or not, their War on Cops is being governed by a timeless economic principle — one made famous by Ronald Reagan: “If you want more of something, subsidize it; if you want less of something, tax it.”

Back in the day, we used to subsidize careers in law enforcement with an abiding show of gratitude and admiration. Cops were our kids’ heroes, and we were overwhelmingly supportive of the vital work they did. Even Hollywood lauded law enforcement with shows such as “Dragnet,” “Adam-12,” “Hawaii Five-O,” “S.W.A.T.,” “Starsky and Hutch,” “Miami Vice,” “Law & Order,” and the like. On the silver screen, Clint Eastwood’s Harry Callahan was a hero not because of his short temper and itchy trigger finger but because we knew he had a good compass, and we knew the thugs he was up against were a lot dirtier than he was.

These days, though, leftist mayors, city councils, and prosecutors are second-guessing the $50,000-a-year cops who make split-second life-and-death decisions; they’re reallocating funds and removing long-held legal protections such as qualified immunity; and they’re siding with Black Lives Matter and its Marxist ilk for one cop-hating protest after another.

Each of these anti-cop measures amounts to a tax on the profession and a disincentive to those who might otherwise consider a career in law enforcement. Is it any wonder that today’s cops are bowing out in record numbers and that tomorrow’s cops are actively searching for other careers?

Take New York City, for example, whose spectacularly effective “broken window” policing approach under former mayor Rudy Giuliani is long gone, having been replaced by the anti-cop, pro-crook policies of leftist Bill de Blasio. Cops in that wreck of a city are now leaving the beat in record numbers, as anti-police animus runs rampant and every violent encounter with an arrest-resisting thug seems to invite another BLM protest.

The New York Post’s Dean Balsamini has the grim numbers. “More than 5,300 NYPD uniformed officers retired or put in their papers to leave in 2020 — a 75 percent spike from the year before, department data show,” he writes. “The exodus … saw 2,600 officers say goodbye to the job and another 2,746 file for retirement, a combined 5,346. In 2019, the NYPD had 1,509 uniformed officers leave and 1,544 file for retirement, for a total of 3,053.”

What a difference a generation makes. As Heather Mac Donald reports, “Giuliani … presided over a 62 percent drop in major felonies from 1994 through 2001 … [but] New York City in 2020 experienced an unprecedented one-year increase in homicides and shootings. Through December 27, 2020, the number of murders was up 41 percent from 2019 and 53 percent from 2018.”

Former NYPD commissioner Bernie Kerik, for one, has seen enough. “No police officer should work in a jurisdiction where they do not have the support of those they work for,” he tweeted. “Beginning today, I will no longer recommend young people consider the NYPD as a career.”

And it’s not just New York. The same is true in Philadelphia, whose police department “currently has 268 vacancies and is expecting even more shortages in the near future,” and in neighboring New Jersey and nearby Baltimore, both of which are dealing with serious recruiting and retention shortfalls.

Pat Colligan, president of the New Jersey State Policemen’s Benevolent Association, invoked Newton’s Third Law. “Every action has a reaction,” he said. “When you vilify every police officer for every bad police officer’s decision, [people] don’t want to take this job anymore.”

How far left will this anti-cop pendulum swing? How badly will it disincentivize good people from going into law enforcement? And how much long-term damage will this do to our cities, our communities, and the Thin Blue Line? This is the Left’s War on Cops, but the answers to these questions affect us all.