Atlassian follows Meta flattens Engineering org, increases team size to 15-18
afr.com
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Corporations who noticed that and started to limit the number of middle managers in the chain to 11, this caused lower ranks of middle managers to only lose their managerial status in the system, while still remaining being managers with the same titles and compensation - "dark management" / "shadow management" ;)
I remember many years ago Intel fired sevral thousands of middle managers to shorten the command chain, and improve decision making.
In my past life at one of those as a direct manager of ICs, I had 12 direct reports, while my manager, and their manager each had 4 or 5. There was definitely room to flatten things a bit. That said, 15-18 is far too many for a single manager to handle, IMHO. If you're managing ICs, you're still (hopefully) using your hands-on experience to provide guidance and mentorship and also staying in touch with technical discussions. With 18 reports, you're basically have no time to really dig into everything, and end up just being the performance monitor.