But how to "Fragment the market legally"? Breakups lead to more monopolies [1]. Could the tax code be manipulated to achieve the desired effect? A market share tax could tax revenue of large corporations (revenue >= $1B [2]) on products and services that are over X% market share at Y%. With X=40% and Y=80%, then:

$4.2B revenue with 40% market share has $0 market share tax and keeps $4.2B; $5B revenue with 50% market share has $800M market share tax and keeps $4.2B; $7B revenue with 80% market share has $2.8B market share tax and keeps $4.2B;

This would reduce the incentive to grow market share above the threshold. A 40% threshold allows for two companies to max out market share and a 30% threshold allows for three companies to max out market share.

[1] https://en.wikipedia.org/wiki/Breakup_of_the_Bell_System [2] https://www.gartner.com/it-glossary/smbs-small-and-midsize-b...