Financial history may not be poetry, but the pattern of booms and busts has a certain rhythm. It is rare, though, that it matches quite so well as two tech bubbles separated by 15 years, those of China today and the Nasdaq in 2000.

It is not just that both sped up as they inflated, or that private investors piled in, or that money was easy. These features are common to bubbles across the centuries. Both had a wave of IPOs as companies tried to take advantage of seemingly insatiable demand for overvalued stocks, too, but high prices always generate their own supply.

The most surprising similarity is the level of the index itself, with the Nasdaq’s dotcom peak of 5,133 just below the Shanghai Composite’s recent high of 5,178, and the rise in the two remarkably close (see chart).