AMERICA’S TECH giants make ungodly amounts of money. In 2021 the combined revenue of Alphabet, Amazon, Apple, Meta and Microsoft reached $1.4trn. These riches come from a wide and constantly expanding set of sources: from phones and pharmaceuticals to video-streaming and virtual assistants. Analysts expect the tech quintet’s combined sales to have surpassed $340bn in the first three months of 2022, up by 7% compared with the same period last year. In a quarterly ritual that kicks off on April 26th, when the big five start reporting their latest earnings, the staggering headline numbers will once again turn into headline news.

Big tech firms are understandably eager to trumpet these impressive figures, as well as their diverse offerings. They are considerably more coy about how much many of their products and services actually make. Annual reports and other public disclosures tend to lump large revenue streams together and describe them in the vaguest terms. Last year, for example, the five giants’ sales were split out into 32 business segments in total. That compares with 56 segments for America’s five highest-earning non-tech firms.

The opacity makes business sense. Keeping rivals in the dark helps ensure that they will not try to replicate a prized business unit and eat into its margins. Andy Jassy, Amazon’s boss, has lamented at the prospect of breaking out his firm’s financials because they contain “useful competitive information”.

Annoyingly for Mr Jassy and his fellow tech barons, the veil of secrecy is getting thinner. Regulators, lawmakers and investors see it as a problem, and are calling for more transparency about everything from how big tech’s payments platforms work to the amount of carbon emissions the companies belch out. And new sources of information are emerging, from brokers’ reports, hedge-fund analyses and, most revealing, antitrust court cases brought by would-be competitors and competition regulators around the world. All these are bringing to light details about the inner workings of big tech.

To understand it all, The Economist has rifled through court documents, internal emails, analyst notes and leaked files about Alphabet, Amazon, Apple and Meta (Microsoft has managed to avoid antitrust scrutiny this time around, so secret information about its finances is scarcer). What emerges is a picture of big tech in which the titans appear more vulnerable than their superficial omnipotence suggests. Their secretive profit pools are indeed deep. But the firms’ finance secrets betray weaknesses, too. Three stand out: a high concentration of profits, waning customer loyalty and the sheer sums at risk from assorted antitrust actions.

Start with the profit pools. The biggest of these tend to be transparent. The iPhone remains Apple’s profit engine, Amazon rakes in most of its money from cloud computing and Alphabet and Meta couldn’t survive without online advertising. The firms are considerably more coy over disclosing details about their smaller but fast-growing units.

Perhaps the biggest untrumpeted sources of profits for Alphabet and Apple are their app stores. The firms take a commission on all in-app spending on these platforms, usually of around 30% (though in a bid to appease regulators, they are increasingly offering lower rates for small developers and those whose apps rely on subscriptions). The revenue streams are middling. In 2019 they were around $11bn for Google, according to one case brought against it in America by a group of state attorneys-general. Analysts estimate th