Asset-price booms are a source of cheer, but also anxiety.
There are two immediate reasons to worry.
First, markets have been steadily rising against a backdrop of extraordinarily loose monetary policy.
Central banks have kept short-term interest rates close to zero since the financial crisis of 2007-08 and have helped depress long-term rates by purchasing $11trn-worth of government bonds through quantitative easing.
Only now are they starting to unwind these policies.
The Federal Reserve has raised rates twice this year and will soon start to sell its bondholdings.
Other central banks will eventually follow.
If today's asset prices have been propped up by central-bank largesse, its end could prompt a big correction.
Second, signs are appearing that fund managers, desperate for higher yields, are becoming increasingly incautious.
Consider, for instance, investors' recent willingness to buy Eurobonds issued by Iraq, Ukraine and Egypt at yields of around 7%.
But look carefully at the broader picture, and there is some logic to the ongoing rise in asset prices.
In part it is a response to an improving world economy.
In the second quarter of this year global GDP grew at its fastest pace since 2010, as a recovery in emerging markets added impetus to longer-standing upswings in Europe and America.
As our special report this week argues, emerging-market economies have come out of testing times in far more resilient shape.