Blog #28: Too Chicken to Challenge Your Assumptions?
When was the last time someone in your organisation genuinely challenged your planning assumptions?
Actually – let me back up. Have you even documented your planning assumptions?
If your S&OP or IBP process doesn’t explicitly track the assumptions behind the numbers, stop here. Go and read my earlier blogs on assumptions (Blogs #8 and #10). Seriously. Your forecast is only as good as the assumptions underneath it, and if nobody’s writing them down, you’re planning on vibes. Fix that first. Then come back.
Right. For the rest of you – when was the last time someone genuinely challenged those assumptions?
Not a polite “have we considered...” but a proper challenge. The kind that makes people squirm. The kind that might actually change the plan.
If you’re struggling to remember, you’re not alone.
The Problem With Human Contrarians
Every organisation needs a devil’s advocate – someone who pokes holes in assumptions, questions the consensus, and asks the uncomfortable “what if” questions before reality does it for you.
The problem? Being that person has a cost.
Challenge the sales director’s volume assumptions and you’re “not a team player.” Question the supply plan’s lead time assumptions and you’re “being difficult.” Push back on the CEO’s growth targets and – well, that’s a career-limiting move (at best).
So people don’t. They nod along. They let weak assumptions slide. And the plan rolls forward on foundations nobody examined – until reality examines them for you.
I wrote about this in my Hubble Telescope blog – one wrong assumption cost NASA $50 million to fix. In IBP, the stakes might be lower, but the pattern is identical. The assumption nobody challenged is usually the one that bites.
Find a Colleague With Nothing to Lose
Here’s where AI earns its keep – not crunching your numbers, but challenging your thinking.
AI has no ego. No promotion to chase. No relationship to protect. No reason to nod along politely when your assumptions don’t stack up.
It will tell you your lead time assumptions are based on conditions that haven’t existed for six months. It will point out that your demand forecast assumes market share growth in a segment where three new competitors just launched. It will ask why your supply plan assumes full workforce availability when it’s the Christmas/New Year period.
No politics. No awkwardness. Just challenge.
Try This
Pick your most important planning assumption – the one the whole forecast leans on – and have a conversation with AI. Don’t just ask once. Push back on its response. Argue with it. Treat it like the sparring partner your team won’t be:
“Our plan assumes [specific assumption]. Tell me why that’s wrong.”
Then when it responds: “You’re being too polite. What’s the scenario where this assumption fails badly? Be brutal.”
Then: “If I had to defend this assumption to a sceptical CFO, what’s the weakest point in my argument?”
You might be surprised how quickly it finds the blind spot your team has been walking past for months – and the best thing, you don’t have to divulge any confidential company info.
It’s Not About the Tech
This isn’t about replacing human judgement. It’s about supplementing the challenge that humans find too uncomfortable to provide.
The best IBP processes have genuine challenge built in. If yours doesn’t – because politics, hierarchy, or just human nature gets in the way – now you have an option that sidesteps all of it.
The assumption you didn’t challenge is the one that will bite you. Your call whether you’d rather find it now – or wait for it to find you. And trust me, it has teeth.
I don’t write these to chase work. I write them because someone should be saying this stuff out loud. Take it, use it, share it – I don’t mind. And if you want more, there’s plenty where this came from at www.planninglab.co.nz/blogs
#IBP #S&OP #ArtificialIntelligence #DemandPlanning #SupplyChain #BusinessPlanning