How Big Was the 777x Miss?
How Big Was the 777x Miss?
Ada re-derives this chapter’s own numbers step by step, at full precision
ADA · CALCULATION AUDIT
How Big Was the 777x Miss?
In the early 1980s AT&T asked McKinsey to forecast the year-2000 mobile phone market, and the answer came back at 900,000 units. The actual number topped 700 million. The chapter calls the miss “about 777x” in one place and “nearly 1,000x” in another, which reads like a contradiction — so this audit re-runs the ratio to ask exactly how big the miss was, and whether those two figures really disagree.
Companion to the chapter IoT History — every number here comes from that chapter.
See the relationship before changing it
The figure reads from left to right. The blue card is actual market size. The middle card applies this page's rule. The green card is forecast ratio. Walk the arrows once: set the input, apply the rule, then read the result with its unit.
The retained audit below checks several chapter fixtures. This model keeps those stated values fixed and changes only actual market size, so the numeric fixture does not switch without explanation.
Derive the baseline in four named moves
- 1
Name the input. The chapter baseline is 700 million phones.
- 2
Name the relationship. ratio = actual million phones / 0.9 million forecast
- 3
Substitute with units. 700 / 0.9 = 777.78 times
- 4
Read the result. Keep the unit beside the value. Use it only inside the technical boundary on this page.
Predict, then change actual market size
Try Predict the direction of ratio = actual million phones / 0.9 million forecast. Test another actual market size, then compare forecast ratio.
Observe The ratio grows directly with the actual market because the nine-hundred-thousand forecast stays fixed. Reset actual market size to 700 and compare forecast ratio.
Explain The ratio grows directly with the actual market because the nine-hundred-thousand forecast stays fixed.
Check yourself
What should you do before trusting a moved-control result?
What does this small model leave out?
Ready: use the stated baseline inputs, then compare each displayed result.
Ada: The chapter says McKinsey’s 1983 forecast of 900,000 mobile phones missed the year-2000 reality of 700 million by “about 777x” in one place and “1,000x” in another. Those are not a contradiction — they are the same miss rounded at two different scales. Let me show it.
Given a prediction of 900,000 units and an actual of 700,000,000 units:
- As a plain ratio:
700,000,000 / 900,000 = 777.78, so the actual market was about 778 times the forecast. - As an underestimate factor, comparing the shortfall to the forecast:
(700,000,000 - 900,000) / 900,000 = 699,100,000 / 900,000 = 776.78, which the chapter rounds to 777.
The precise figure is about 777x and the headline “1,000x” is simply its order-of-magnitude rounding — and for forecasting the lesson survives either rounding: a linear estimate anchored to a $4,000 handset missed an exponential adoption curve by nearly three orders of magnitude, so a paradigm-shift forecast must be judged on its growth model, not on its decimal places.
Every number above is taken from the chapter’s own material and re-derived step by step.