Today, let’s talk about central bankers, insane interest rates and how U.S. taxpayers could benefit a bit from the lunacy infecting the world’s markets.

Let me explain. Once upon a time, the world’s central bankers were thought of as sober bureaucrats who were supposed to rein in financial markets’ animal spirits. In the words of former Fed chairman William McChesney Martin, a central banker “is in the position of the chaperone who has ordered the punch bowl removed just when the party was really warming up.”

But that was in 1955. In 2015, central bankers are spiking the punch rather than taking the bowl away. That’s why interest rates in the United States and Europe are so low that they seem to have been determined by drunks who have forgotten how to count.

My favorite example is Switzerland, whose 10-year government bonds, denominated in Swiss francs, currently yield . . . nothing. You pay 115 percent of face value to buy a 10-year, 1.5 percent Swissie (as bond-biz types call it) that will pay you a total of 15 francs of interest through 2025, when it comes due and pays 100 percen of face value. So unless you have some compelling reason to own a Swiss franc security — you’re an oligarch stashing capital abroad, or a trader, or you think the end of the financial world is at hand — you have no business buying a 10-year Swissie.

We’ve got other European governments — Germany, the Netherlands and France — whose euro-denominated 10-year bonds yield less than 1 percent. This makes 10-year U.S. Treasury securities, yielding all of 2 percent, look like great investments. Even though they aren’t.

It’s a horrible time to be a saver, especially a retiree trying to live off interest income. But central bankers don’t care about savers these days. They’re trying to stimulate their countries’ economies with ultra-low interest rates and by holding down the value of their currencies to help boost exports and reduce imports.

But it’s a great time to be a borrower. Giant companies — Apple and Microsoft come to mind — are issuing vast quantities of debt, locking in today’s ultra-low rates for years, if not decades. Apple, which last year sold euro securities at rates lower than equivalent U.S. securities, this week sold 9¾-year Swiss franc paper carrying an interest rate of 0.28 percent. That’s 85 percent less than the U.S. government pays on 10-year Treasury notes.

Microsoft is doing some interesting borrowing, too. This week, it sold $2.25 billion of 40-year bonds. Why is that interesting? Because the vast majority of borrowers — including the U.S. Treasury — don’t sell securities with maturities of longer than 30 years.

What surprised me is that the 40-year Softie bonds carry an interest rate of only 4 percent, according to S&P Capital IQ. That’s just a quarter-point higher than the 3.75 percent Microsoft paid on the $1.75 billion of 30-year bonds that it sold.

If I ran the U.S. Treasury, which doesn’t sell securities with maturities of longer than 30 years, I would peddle 40-year bonds before the markets sober up. The 30-year Treasury currently yields about 3 percent. For technical reasons, the spread between 40-year and 30-year Treasurys would probably be way less than the spread between 40- and 30-year Softies. So 40-year Treasurys would probably go for 3.1 percent or so. That would be a total bargain for taxpayers — especially when you consider that a year ago, 30-year Treasurys were yielding more than 4 percent.

To its credit — no pun intended — the Treasury has been forgoing the chance to load up on short-term debt, which costs it essentially nothing, and has been lengthening the “weighted average maturity” of Treasury debt to 68 months from less than 50 months in 2009. Thus to some extent, the Treasury has been locking in today’s low long rates.

I would dearly love to see the Treasury, which declined to comment, start selling 40-year or even 50-year bonds. If that happens soon, while rates are still so low, we taxpayers should treat the Treasury’s debt peddlers to a big bowl of punch. With as much alcohol as they’d like.