Thursday, September 22, 2011

Span of Controls

Coincident with the launch of Startup Engineering Management, I'd been asked to help out at a few startups, two of which were Obvious and PlayMesh. A common question that came up at both places was: What's the appropriately wide span of control in management.

I believe the answer to that question is: "It depends." If you look at industry wide span of controls, they're somewhere around 6 to 1. That is, every 6 engineers will have a manager. If you examine that carefully, however, what you'll notice is that this arises typically in larger corporations. In those corporations, what's happening is that aggressive go-getters who don't get promoted will quickly leave, and the only way to retain such people is to give them management positions long before they're ready. (An alternative is to set up a separate engineering ladder, which was advocated as far back as The Mythical Man Month. That doesn't work as well as its advocates will have you believe) Effectively, at large corporations sporting a 6:1 engineer/manager ratio, what you are doing is training engineering managers on the job, where the manager is essentially still expected to perform individual contributor duties in addition to doing management.

At well-run startups where most engineers who are brought in do not need a lot of coaching, the appropriate span of control is closer to 20 engineers. At that level, the manager can't do a lot of coaching, but more importantly, he can't possibly do any micro-management, which is irritating if you've hired high performance engineers. Essentially, the manager has to lead by setting direction, not provide management or mentoring at the task level. That doesn't mean he can be non-technical, because you need to be capable of understanding detailed software/hardware architecture in as much as it affects your product. To give an extreme example, Wayne Rosing in his early days at Google had all 100 engineers directly reporting to him. Having participated in those structures before (as described in An Engineer's Guide to Silicon Valley Startups), it was extremely exhilarating, and yet Wayne (and Bill Coughran) always knew what the problems were and how they could help every time I came to one of them with one (very often, the way they helped was to send a one word e-mail: "Approved.").

If you're promoting engineers into management positions who have not managed before, you will need to be closer to the industry 6:1 ratio. However, if you're hiring a manager from outside, your bar needs to be a lot higher: they need to be able to handle a span of control of 20:1. Many startups do not hold incoming managers to that standard, and therefore end up with poor management. I'll give you a concrete example: Facebook does not hire managers from outside, because they've discovered that the practice does not work. However, they do hire directors from outside with some degree of success (though less so than with directors who were promoted from inside), and one reason for that success is that most directors hired from outside have already proven themselves capable at the 20:1 ratio.

At the tech lead level, however, you probably will still need the 6:1 ratio. But tech leads are by their nature not going to provide the full range of management functions.

Is there a way to short cut this process? Yes. One of the best tips in Startup Engineering Management is actually one that came from Yishan Wong: when hiring engineers, try to look for engineers who've managed before and are willing to come back as an individual contributor. This lets you promote from within once you need managers, and also gives you managers that don't consider management an more important job than engineering.

One interesting note is that these numbers are extremely similar to what the U.S. military uses in the army: a squad leader commands a group of 8, and a platoon commander commands three squads for a group of 24. The squad leader is very much like a tech lead, and the platoon commander is the lowest level officer in the army. While you might argue that military jobs aren't as cognitively challenging or creative, I'd counter that you should be also much more demanding in your recruiting process than the military, hence the similarity.
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