

Norvig's Law - parenthesis
http://norvig.com/norvigs-law.html

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cperciva
Peter Norvig is wrong. He claims that _"Any technology that surpasses 50%
penetration will never double again (in any number of months),"_ but the raw
foodism reached 100% penetration millions of years ago, fell off sharply after
the discovery of fire, and has doubled several times in the past couple of
decades.

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rocha
It depends on the unit that is doubling. From how I read the claim, Peter
Norvig is using penetration percentage as such unit. Once you reach 50%,
doubling means 100%, which is very unlikely since it is almost certain that
somewhere in the world there is someone that does not use certain technology
(meaning writing, clothing, radio, cellphones or whatever...). In short: the
claim is just a clever joke :)

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aneesh
Yes, we got the joke. But suppose in 50 years we come up with a cool
technology that is so good it drives cell phone penetration down to 1% (ie
young people growing up then never buy cell phones). Then cell phones can make
a comeback and double to 2%. And double _again_ to 4%, etc.

~~~
etal
But then, as far as business is concerned, hasn't it already been shown that
the cool new technology was a replacement for cell phones? Assuming CoolTech
isn't subsequently found to cause the sudden onset of rickets in its users (or
whatever), the market for [stuff that stuff that satisfies the need for cell
phones] is still saturated. The market won't start roaring again the way it
was; cell phones can only cannibalize CoolTech's portion of the market.

The latent Apple analogy is making me uncomfortable now, so I'll stop here.

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malkia
Any technology that surpasses 33.3333% penetration will never tripple again
(in any number of months).

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timtrueman
I know a few people that carry two cell phones... It's a technicality but you
can have more than 100% market penetration. Does that count?

"Luxembourg racked up 158 mobile subscriptions per 100 people, closely
followed by Lithuania (127) and Italy (122)." Source:
<http://news.bbc.co.uk/1/hi/technology/7116599.stm>

~~~
etal
The article's not that long! Here's the second half:

 _To be clear, it all depends on what you count. If you're counting units
sold, you can double your count by selling everyone 1 unit, then 2, then 4,
etc. (In Finland I understand that cell phone usage is above 1 per capita, but
still growing.) If you're counting the total number of households that own the
product, you can double your count by doubling the population, or by
convincing everyone to divorce and become two households. But if you're
counting percentage of people (or households), there's just no more doubling
after you pass 50%._

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timtrueman
Right, I actually did read that far. I'm just trying to illustrate unless he
defines it in a way the excludes cases like that, I'm not sure you can call it
a law...a generalization with exceptions, maybe. As his law is written, the
cell phone example kinda disproves it. I think the problem is that paragraph
you quoted can't easily be reduced to language that fits in that blue box.
Just playing devil's advocate...

~~~
etal
A worthy aim, but the whole idea of the "law" is Norvig's implied definition
of what market penetration means. If 75% of the people in the world have never
owned a smartphone, then doubling the number of smartphone owners is a big
accomplishment, and doubling it again means you've introduced 100% of the
world to smartphones. The number of phones you've _sold_ is not the concern,
it's the proportion of people whose needs have been satisfied. (At least,
that's what Norvig cares about.)

Without going down the route of identifying a new market, once more than 50%
of the population in question has had its needs met, that market is mature --
its growth has reached a point of inflection, and no amount of pushing on the
part of the existing industry will make the product continue to change lives
at the rate it used to. The opportunity that was there has already been
identified and seized.

Now, if everyone in Finland has a personal cell phone, and another 25% also
keep a separate cell phone for business use, it's suddenly worth redefining
what the market is. Should the industry try to double market penetration of
business-only cell phones, now? Why isn't one phone enough, and could a new
product meet these separate needs better? Or alternately, some people keep two
phones with different plans, and switch between them to keep the total bill
down -- breaking that confusopoly is another business opportunity worth
identifying, but tracking units/plans sold instead of actual market
penetration by population will mask it.

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bayareaguy
This law only holds true for very broad catagories of technologies e.g. use of
fire, hydraulics, electricity, radio, genetics, atomic power, nanotech, etc.

If you try to apply the it to something more narrow you run into the problem
that many specific technologies come in and out of favor depending on market
conditions.

