US dollar owes its strength to one simple thing: the world's need to repay a mountain of debt
World debt had reached above 210pc of global GDP by 2013, up from 180pc in 2008 - much of it in greenbacks that have since risen in value
The world has taken on a huge amount of dollar-denominated debt in recent years, but with the pace of global economic growth lagging the rate of increase in borrowing, the burden of that debt is rising.
Borrowers are left to seek dollars in their attempts to obtain the currency in which they must try to fulfil their obligations.
Since 2008, "banks and bond investors have increased the outstanding US dollar credit to non-bank borrowers outside the United States from US$6 trillion to US$9 trillion", a Bank for International Settlements (BIS) working paper said in January.
That US$9 trillion figure was striking enough to elicit a further mention in March's BIS Quarterly report.
It is worth noting too that the January working paper shows that the equivalent figure in 1998, a year in which much of Asia endured a financial crisis, was only just over US$2 trillion.
But the absolute level of global dollar-denominated debt is less important than the fact that the stock of debt is growing as a percentage of world gross domestic product. The debt is arguably becoming more burdensome.