Bitcoin's notorious volatility was enriching bulls on Monday.

The bitcoin price has climbed 17% over the past 24 hours to clear $40,000 for the first time since mid-June.

The largest cryptocurrency by market value, which dipped below $30,000 as recently as last week, has now climbed for a sixth straight day.

Analysts in digital-asset markets attributed the latest climb in part to a short squeeze: Traders who had previously bet on further price declines scrambled to get out of their positions, while others were liquidated due to margin calls.

So far in 2021, bitcoin is up 38%. That's more than double the 18% year-to-date gain in the Standard & Poor's 500 Index of large U.S. stocks.