For people who hope to retire someday, maybe in their mid-90s, the plummeting stock market is hard to look at. But the market is sending a signal that the government should heed — not thwart.

The biggest problem with avoiding a deep economic hit from corona­virus — other than the tragic fact of the virus itself — is that the economy is already so ­hyper-stimulated that it is­ ­going to be really hard to induce people to spend their way out of this one.

Last week, with the Dow Jones Industrial Average down 2,500 points in a month, the Federal Reserve tried to go big and bold. It made an “emergency” cut to interest rates, the first time since the ­financial crisis a decade ago.

The half-a-point cut brought the rates at which banks can borrow from each other down to 1.25 percent, a rate that would indicate an economy already in deep recession and in need of a rescue.

But it didn’t “work,” in that the stock market continued to fall. By the end of the week, the Dow had shed another 1,200 points.

Despite a healthy jobs report for the month of February, with more than 270,000 people hired, the stock market is telling us something you probably already figured out yourself: Unless you own a hand-sanitizer company, contagious disease isn’t good for the economy.

The first part of why the rate cut didn’t work is obvious. A cut in interest rates is supposed to spur companies and people to borrow money and spend it. Mortgage rates are now at their lowest rate ever, just above 3 percent. But companies aren’t going to make big investments when their supply chains are broken. Drugmakers and toymakers alike can’t sell to the American consumer when Chinese workers can’t get to work to make the drugs and the toys.

An interest-rate cut isn’t going to spur you to take that spontaneous trip to Italy right now. And if you are worried that the virus will cause you to miss work, you are unlikely to buy a house.

The other reason is less obvious — and, if the virus does keep people quarantining themselves long term, it will be a bigger problem. It’s hard to stimulate this economy back to health, ­because it’s been overstimulated for more than 10 years.

Rate cuts to induce people and companies to borrow more? American families have already maxed out their credit cards.

This isn’t a metaphor for something; they have literally maxed out their credit cards, owing $4.1 trillion on consumer debt other than mortgages, up from $3.2 trillion in 2008 (after adjusting for inflation). Even before coronavirus, delinquency rates on this type of debt were inching up.

OK, well, what about fiscal stimulus? That is, instead of cutting rates to induce people to borrow more, the government could do that borrowing itself, and then give people the money directly. Last week, President Trump suggested a payroll-tax cut, which is exactly that.

With a trillion-dollar annual budget deficit, though, long ­before the virus hit, the government is already doing that, too, and has been for years.

If coronavirus keeps planes grounded and trains empty for much longer, the feds will have to take measures ­beyond the $8.3 billion Congress just approved for direct disease-control spending.

Travel-industry workers will be without work and thus will need unemployment insurance, as will people who work on assembly lines that are missing imported parts (and customers).

And Congress will have to make tough calls: Should airline shareholders, or taxpayers, take the hit from a disaster that is out of the airline industry’s control? State and local governments, too, will lose tax revenues and face budget cuts, when many have barely recovered from the 2008 recession.

But it’s going to be hard to get big results by ramping up spending in a real emergency, when both Congress and the Fed, through their loose interest-rate and deficit-spending policies, have been acting like it’s an emergency for more than a decade.

Will we see a $2 trillion budget deficit — or interest rates at negative six? Long before corona­virus, Washington had gone way beyond what anyone would consider normal.

The Fed and Congress, in that sense, are like parents stuck with a house full of quarantined kids to feed. When they open the cupboard for the emergency food stash, they are surprised to find only an empty bottle of whiskey.

Nicole Gelinas is a contributing editor of City Journal. Twitter: @NicoleGelinas