FORTUNE — In a chart posted on Twitpic Monday, Asymco‘s Horace Dediu shows that the multiple of PCs sold to Apple (AAPL) Macs sold has been falling steadily since it peaked in 2004 and is approaching the ratio of 1985.
What turned the tide? My best guess is the release of iTunes for Windows in 2003 and the subsequent spread of the so-called iPod halo effect. Note also the drop in the PC-to-Mac ratio in 2007, the year the iPhone was introduced.
UPDATE: On Wednesday, Dediu filed an article about this ratio, noting that when iOS devices are included in the comparison, Windows’ advantage over Apple drops below 2 — a multiple that is likely to be reduced to parity with a year or two.
Below: Dediu’s updated chart.