okay digging in to my vague memories - it was claimed as 25 hours, and posted by a charismatic-ish internet gadfly in the early 2000s, Philip Greenspun: here's a slashdot link about the story: https://developers.slashdot.org/story/00/11/06/1448235/green... but I didn't dig up the original. I have no idea if Philg referenced data in his essay, but I kind of bet he did, it was his style. Not that his style was to fairly reference data mind you.
20-25 hours makes more sense - especially in an era before a lot of productivity tooling like Slack, Git, Zoom, Notion/Confluence, and Asana/Jira was created or normalized, and development processes were way less nimble and iterative than they are today.
I'd be curious to see similar data today - my gut is saying that the hours spent in meetings for IC engineers (Staff and below) is probably lower today than it was 25 years ago because of the productivity gains and changes in management culture, but I'd need data to make such a qualification.
It is also interesting to go thru that slashdot thread and see how similar the conversations were back then to those we still see today.
Slack definitely changed things. I'd guess largely for the worse when it comes to knowledge work. But it definitely everted meeting time into all the time, which means there's less scheduled meetings. Closing the door to work uninterrupted is harder now though
