Putting together a list of the ten biggest heists turned out to be a much more complicated task than one would expect. The first issue that came up was deciding what constitutes a "heist.”

We omitted any cases in which a government took money from its own bank, as happened before the fall of Nazi Germany or Iraq. The same rationale applies to corruption by a government leader such as former Philippines President Ferdinand Marcos and his wife Imelda. We also took out art heists, since values for stolen famous works do not reflect the actual market value of the stolen goods. For example, if someone stole the Mona Lisa, it could be valued at an astronomical figure, but no one would buy it for anything near what it’s worth. Its real value would be what it could fetch on the black market, which would be very little, or in reward or in ransom.

The next issue was the amount stolen. Although news reports used specific figures for the amounts believed to have been taken, numerous problems often exist with such numbers. As we’ve seen with the Antwerp diamond heist, the amounts given are generally estimates and sometimes it’s hard to put an exact number on the losses, such as with a safe deposit box job. Even when a single business, such as Harry Winston, was hit, the question arises whether the amount cited was the wholesale value or the retail value and how much the thieves could expect to make fencing such goods.

Another problem pertains to currency exchanges. For instance, the estimate given by police at the time of the Antwerp diamond heist was more than £100 million. A prosecutor later alleged it was closer to £400 million. We used the exchange values at the time of the heist, but that lowers the dollar amount of the Antwerp diamond heist versus the Harry Winston heist as the value of the euro against the dollar went up in the meantime, making the two amounts look much closer in dollars than they do in euros.

The Graff Diamonds heist happened after this chart had first been drawn up, knocking the Brink’s-Mat heist from the "World’s Ten Biggest Heists.” Brink’s-Mat was the theft of three tons of gold worth $37.5 million at the time. It took place on November 26, 1983, in London.