FORTUNE — Everybody who follows the computer industry knows that Apple’s (AAPL) Mac trails far behind its Microsoft (MSFT) Windows-based competitors — Hewlett-Packard (HPQ), Dell (DELL), Lenovo and the like — in terms of worldwide PC shipments.

But who knew what the market looked like in terms of economic value?

Leave it to Asymco Horace Dediu to boil it down to a pie chart (above) and a simple ratio: Apple sells 5% of the world’s PCs and takes home 45% of the profit.

“The real problem for the PC vendors,” he writes in an article posted Tuesday, “is not that they have such low margins — they’ve had low margins for decades. It’s that the volumes which ‘made up for’ low margins are disappearing. Apple is not immune to a gradual erosion of Mac volumes, but they have positioned themselves for growth with devices and content commerce and services. They have essentially ‘escaped’ PCs and indeed caused the need to escape in the first place.

“The problem is what could the others do? It seems all they can do is depend on Microsoft getting their strategy right.

“Sounds risky.”

Link: Escaping PCs.