Some Australians are burying it. The Swiss might be hiding it. The Germans are probably hoarding.

Banks are issuing more notes than ever and yet they seem to be disappearing off the face of the earth. Central banks don't know where they have gone, or why, and are playingdetective, trying to crack the same mystery.

Following the money trail can often mean encountering a motley cast of characters that wouldn't look out of place in a detective novel. Dollar bills are often vital grease forcriminal gangs and tax cheats. They are also popular with collectors who worry about a future collapse of the financial system.

Bankers aren't just hunting down cash to satisfy their own curiosity. If central banks don't know how much cash is out there, they could print too much currency and riskinflation.

In September, a court in Germany ruled on a case brought by a man who stuffed more than 500,000 euros in a faulty boiler only to see it incinerated when a friend made a fix ona cold day while he was on vacation. The man sued his friend for the value of the lost bank notes plus interest. He lost.

The Bundesbank thinks more than 150 billion euros are being hoarded in Germany.

The Reserve Bank of Australia's Note Issue Department decided to take an unusual approach: could fire-damaged bank notes help to determine how much money is being hoarded?Analysts even devised an equation based on the value of claims submitted by households for new bank notes to replace those that had been damaged by fires.

It didn't work.

Officials at the Swiss National Bank ran with another theory: hoarded bank notes should wear out less because they aren't being used for everyday transactions.

Demand for high-denomination bank notes tends to rise when interest rates are low, households feel distrustful of the banking system or people want to make transactionsanonymously.

Generally, SNB officials found that hoarding of Swiss francs jumped around the year 2000, likely motivated by fear of the Y2K bug infecting computer systems, the bursting ofthe dot-com bubble, the September 11 terrorist attacks and introduction of the euro. The financial crisis that began in 2007 encouraged people to stash even more.

"Our sense is that we're in the same boat as a lot of other central banks out there," said Christian Hawkesby, assistant governor at the RBNZ. "We can't fully explain whyholdings of cash are rising and where they are going."

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The World's Cash Is Disappearing. Bankers Aren't Sure Where ItWent. (https://www.wsj.com/articles/the-worlds-cash-is-disappearing-bankers-arent-sure-where-it-went-11576184491)