The main difference with Microsoft is that Apple does not have a monopoly in phones like Microsoft had with PCs. Apple phones make up only 13% of the phone market.
Colloquial definitions of monopoly do not matter when it comes to antitrust laws[1]:
> 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. That is how that term is used here: a "monopolist" is a firm with significant and durable market power.
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> Apple phones make up only 13% of the phone market.
Depends on how one defines "monopoly". Back in the late 1990s, one could theoretically install non-Windows OSes like Linux, Unix or even purchase an Apple Mac. But yes, in practice Microsoft commanded the market and abused its market power.
You could argue that users technically have a choice to switch to Android but due to network effect (e.g. your family/friends all use iOS) and lock-in features like iMessage and Facetime, it's often a false choice.
Every time App/Play store fees are discussed, it devolves into unproductive hair-splitting over the word monopoly. The proper term is captive market.
> Captive markets are markets where the potential consumers face a severely limited number of competitive suppliers; their only choices are to purchase what is available or to make no purchase at all
> 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. That is how that term is used here: a "monopolist" is a firm with significant and durable market power.
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> Apple phones make up only 13% of the phone market.
iOS has 60% of the market in the US[2].
[1] https://www.ftc.gov/tips-advice/competition-guidance/guide-a...
[2] https://deviceatlas.com/blog/android-v-ios-market-share