Nobel laureate in economics Paul Krugman says he wouldn’t trust South African billionaire Elon Musk to feed his cat and compares Tesla shares to Bitcoin, Markets Insider reports.

In a new op-ed published in The New York Times on Tuesday, Krugman asks rhetorically if “the Tesla story ever made sense?”

In the editorial, he explains that Tesla isn’t worth as much as other big American companies like Apple or Microsoft because it doesn’t benefit from a product network.

Apple has a whole “ecosystem” of interconnected devices, applications and services for its customers and users, while Microsoft Word and Excel remain reference programs in companies because they are known to everyone and are the benchmark in the field.

Krugman argues that, unlike these big American companies, Tesla does not offer its customers a real benefit in terms of a network of products or services, while noting that the Elon Musk-led electric car maker faces competition from stronger traditional car companies such as like General Motors Ford or Volkswagen.

“It’s hard to see what could have prevented Tesla from locking up the electric car business,” writes Paul Krugman, adding that much of the Musk-led company’s popularity stems from the fact that people perceive its CEO as a “cool guy.”

The Nobel laureate is involved in work with Elon Musk and Tesla

But Krugman says perceptions of the Twitter, Tesla and SpaceX CEO have shifted in recent weeks following a series of controversial decisions by Musk at the social network he took over in late October.

“Given what I’ve seen of Musk’s behavior, I wouldn’t trust him to even feed my cat, let alone run a large corporation,” the Nobel laureate wrote.

He also drew a parallel between the huge hype that fueled Tesla’s stock price spike during the pandemic and Bitcoin’s spike over the same time period, noting that the cryptocurrency has no obvious use other than money laundering, but that its price is rising because of ” a fervent group of true believers.”

This isn’t the first time Krugman has spoken out against cryptocurrencies and the crypto space in general, comparing their rise to the US real estate bubble of the mid-2000s that ultimately led to the Great Financial Crisis and the recession that followed.

Krugman, who won the Nobel Prize in Economics in 2008, noted at the time, however, that a possible collapse of the crypto market would not have the same consequences as the bursting of the housing bubble in the United States, which triggered the crisis that shook the global financial system.