Recently, I mentioned that North Korea — and fears over the prospect of war — was one of the many problems that Wall Street would have to face this fall.

Little did I know that the problem would tease itself days later. The Dow Jones industrial average fell 186 point last Thursday and Friday on precisely those fears.

But the safety of Guam — no offense to its 163,000 residents — isn’t the only thing that can rattle US markets. There’s also the Federal Reserve and the economy.

The economy is listless. It has been for a decade.

Growth in the first half of 2017 was at a rate of slightly less than 2 percent a year. In fact, the economy is doing so poorly that the Federal Reserve had to back off its plan — as I thought it would — to raise interest rates a number of times this year.

Job growth has been picking up. But there hasn’t been a comparable rise in disposable income, so either the jobs numbers or the income figures — or both — are wrong, or the types of jobs being created are substandard and low-paying.

That’s the dicey economic environment in which the Fed is operating. But the central bank’s job is even a bit tougher than that — it is going through what is called the “normalization of the Fed’s balance sheet.”

That’s easy to explain but difficult for the Fed to execute.

In essence, it means that the Fed needs to get rid of the bonds that are on its books from quantitative easing, or QE. First, there’s a possibility that the Fed will botch this operation and create inflation fears that will drive up interest rates.

But even if the unwinding itself comes off without a hitch, there’s a concern that the reversal of QE — which was designed to put liquidity into the economy — will end up being quantitative tightening (QT), a phrase that I think I just made up.

If QE helped the economy grow (and it did, but only a little), then might QT cause an already listless economy to grow even less?

And if economic growth falters some more, what does that mean to a stock market that seems to be taking all the problems today very lightly?