Is the bull market about to turn into a bubble?

livemint.com:

all-time highs (see chart 1). America’s in particular is on an eye-popping run, with the S&P 500 index of large firms having risen in 16 of the past 19 weeks. The value of Nvidia, a maker of hardware essential for artificial intelligence (AI), has risen by more than $1trn in the space of a few months.

Bitcoin hit another record on March 11th. Disorientingly for those who blamed the previous mania on near-zero interest rates, this comes after a brutal campaign by central bankers to yank them back to more normal levels (see chart 2). Once again, every conversation about markets veers unerringly back to the same question.

Is this a bubble? For many, the parallel that springs to mind is not the most recent bull market but that of the late 1990s, when the dotcom bubble inflated. Then, as now, new technology promised to send productivity and profits to the moon, the innovation in question being the internet rather than artificial intelligence. Bulls in the 1990s were correct that advances in telecommunication would transform the world and spawn a new generation of corporate giants.

Yet plenty still ended up losing their shirts—even by betting on firms that went on to be phenomenally successful. The canonical example is Cisco, which, like Nvidia, made hardware crucial for the new tech age. Although in the most recent fiscal year its net profit was $12.8bn, up from $4.4bn in 2000 (both in today’s money), those who bought shares at their peak in March 2000 and are still holding today have taken a real-terms loss of nearly 66%.