Toward the end of Gov. Tim Walz’s April 9 press briefing on the state’s COVID-19 pandemic response, the 24-year National Guard veteran drew on his experiences fighting floodwaters to deflect skepticism about his four-week extension of the stay-at-home lockdown of Minnesota’s economy.

Walz noted that it’s nothing new to erect costly defenses against looming threats, even when we must base our actions on uncertain predictions about the scale of the danger.

“We’ve done this before,” the governor said. “I have been activated and have filled sandbags for weeks that never, ever got wet. They never got wet. We wasted a ton of time and a ton of money. But all of the modeling on the flooding showed us it was going to happen and it made sense to do it … .”

The governor’s reliance on this analogy goes to the heart of what, at bottom, some doubters find unsettling about the economic havoc Walz and other political leaders continue to believe America must inflict on itself in an effort to hold back the coronavirus tide.

The “ton of time” and “ton of money” invested in filling surplus sandbags somehow doesn’t quite seem equivalent to decisions that have set off a staggering economic collapse of unknown but perhaps unprecedented depth.

State officials reported this week that the ranks of unemployment insurance claimants in Minnesota soared nearly sevenfold in just the last month, with about 15% of state workers being idled more or less at once. Latest national estimates project the annualized rate of contraction in economic output at an unheard of 40% between April and June. We’ve achieved “easily the worst stretch of U.S. job losses on record,” according to news reports Thursday.

That’s a whole lot of sandbagging.

Walz, along with Health Commissioner Jan Malcolm and her team of researchers, have taken pains in recent weeks to explain the epidemiological models they have used to project COVID-19 cases and outcomes. Skeptics have questioned the conflicts between Minnesota’s projections and those of other models — along with a steady stream of downward adjustments to the death projections.

The questions are legitimate. The answers, meanwhile, have been illuminating and candid. And the bottom line simply seems to be, as Walz might say, that projecting an epidemic, like projecting a flood crest, is an uncertain affair. It makes sense not to be overly optimistic.

But what hasn’t been much discussed, or much in evidence, is the inquiry and examination Walz and other governors have been using to forecast the cascading economic harm that will eventually be done by shuttering many thousands of businesses and throwing many millions out of work, depending on how long it all lasts. Economic projections are difficult, too, but Walz and the other policymakers seem content to lament the economic pain all around them, and to express their longing for the earliest possible return to normal.

Such noble emotions don’t give much more assurance of a painstaking analysis than a phrase like “ton of money” does. Sympathetic feelings may not produce the kind of rigorous calculation we need as to when the public welfare damage from self-administered economic paralysis will begin to exceed the public welfare gains we can achieve in reducing sickness and premature death.

In short, what we need is a cost-benefit analysis — a determination of when the benefits of an intervention cease to outweigh the harms of its unintended but unavoidable costs or side effects. To determine that, those costs and side effects have to be discussed and examined as carefully as the hoped for benefits of social distancing.

Always controversial and uncomfortable when life-or-death issues are involved, cost-benefit evaluations have become standard in many regulatory processes. Rulemakers are often required to show that a particular safety requirement or pollution standard is worthwhile — after all of its effects are considered. Assessments of “safety and efficacy” for pharmaceuticals and medical devices and therapeutic procedures involve a cost-benefit calculation. The reason drug commercials feature long recitations of horrendous possible side effects is that risks remain even in officially safe and effective therapies. It’s just that the benefit has been judged to be worth those risks.

It simply has not been clear in much of the public discussion and debate over the lockdown that a serious balancing test of this kind has been applied. Instead, we’ve heard many echoes of New York Gov. Andrew Cuomo’s much noted remark, as the Associated Press puts it, “that if all of his sweeping, expensive measures to stem the coronavirus saved one life, it would be worth it.”

There is no reason to question anyone’s motives or best efforts. Much of the problem lies in an asymmetry in the vivid visibility of the ravages of the disease compared with the ravages of the cure. Many, many millions of Americans are in households that have suffered job losses. Many watch helplessly as businesses wither.

But such vast miseries are too enormous and diffused to feel vividly and viscerally. The daily COVID-19 death count — delivered breathlessly by the media in a way it never reports the every day death toll from familiar causes — dramatizes tragedy on a more human scale.

What’s more, with the vast majority of governors having once put in place sweeping lockdowns, which among them now can dare to be the first to relax restrictions? No doubt this political dilemma — and a desire to create safety in numbers — is part of the motivation for the “pacts” now being formed among neighboring states to coordinate plans for reopening their economies.

It might also help to prepare the public for the unknowable results of that risk-taking if leaders talked more candidly about our need to fully consider all the dangers we confront in this struggle.

D.J. Tice is at Doug.Tice@startribune.com.