On 19 August the US Treasury said it will at least double the size of its long-dated bond buybacks, from $2 billion an operation to at least $4 billion, starting on 9 September. It was read almost everywhere as money printing. That reading skips the part where somebody has to fund it.

A buyback is the government buying its own bonds back from the investors holding them. It leaves what Washington owes exactly where it was and changes the shape of the debt instead.

Long bonds come out of private hands and short bills go in to replace them, and the point of that is to bring long-term borrowing costs down. Long yields did fall on the announcement, from a thirty-year rate that had reached 5.3 percent this month, the first time since 2007.

From there most people took one step and stopped. The dollar gets weaker, money gets cheaper, and you own the hard things. Gold, bitcoin, silver and platinum have all risen together this month and the dollar is down 2.4 percent since it began, so the step was well earned.

It is still one step short. Retiring a thirty-year bond and issuing a three-month bill in its place leaves the same debt behind and a much larger amount of short-term borrowing to refinance every few months. Somebody has to buy those bills. Not once, and not only in September.

The difference between the two pieces of paper is time and almost nothing else. A thirty-year bond is a promise to pay the holder back in 2056. A three-month bill is a promise to pay them back before Christmas. Swap one for the other and the government has to return to the market four times a year to borrow the same money over again, and every one of those visits is a chance to pay more than it paid last time.

If that buying is thin, short-term rates rise, and what the government saves on the bonds it pays back on the bills.

There is a buyer for short-dated government paper that did not exist in law two years ago, and it is not allowed to buy anything else.