At which point does a monopoly becomes a monopoly?

There is no need to have a "clear" monopoly like Windows in 1990's to abuse your power and presence in the market.

> At which point does a monopoly becomes a monopoly?

It's generally in the 70-90% range. Right now, it's much easier to argue that Android has a global monopoly.

> There is no need to have a "clear" monopoly like Windows in 1990's to abuse your power and presence in the market.

Well it depends what you mean by "abuse". I mean, even small companies can "abuse" their customers by not building the interoperability their customers want. But we generally prioritize individual freedom, that private businesses ought to have free choice in what they work with or don't. That's important.

That only becomes a problem when consumers aren't able to switch to a competitor. I.e. when there is a monopoly provider. I.e. which controls 70-90%+ of the market.

we're getting close then in usa https://www.counterpointresearch.com/insights/us-smartphone-...

https://www.removepaywall.com/search?url=https://www.wsj.com...

The median in the first chart is 53%. So not really. Apple is just seasonally high in Q4 presumably because iPhones make good Christmas presents. And still below 70%.

> it's much easier to argue that Android has a global monopoly.

Sorta. My understanding is that Google Play has the global monopoly. If it were plain Androids that users bought to own, to do with as they wanted, I'd be much less sombre about where mobile ecosystems are headed (namely, that governments, banks, public transport companies, and many other organisations will require a DRM-locked device if you want to live a normal life, buying bus tickets while passing the algorithmic fraud checks instead of needing to travel to a remaining ticket counter for example). It's barely even the future anymore, bank and transit company apps already mostly only run if you have a Google account and are on a locked-down ("Google Safetynet") device or go to great lengths to hide that you've got full access to your own data on your bought-to-own device

> Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power — that is, the long term ability to raise price or exclude competitors.

https://www.ftc.gov/advice-guidance/competition-guidance/gui...

Presumably the DoJ wouldn't have sued Apple for being a monopoly if it was impossible for them to legally qualify as one?

https://www.justice.gov/archives/opa/gallery/justice-departm...

The DoJ can sue over whatever they want. They also lose suits all the time. So now it's up to a court decision to make the determination, and it may very well be that Apple is not, contrary to the DoJ's assertion.

Sure, but you claimed that they were definitely not a monopoly, which hasn't been determined yet.

If it's not a duopoly, then why there's no competition between the play store and the app store to get developers or users from each other?

The only tariff change ever made on the appstore was as a reaction to an antitrust lawsuit and copied straight to Google. Just that is enough of a proof.