As we will see, the principle that sharing is hard, is very applicable.

Have you ever stopped to think, how many cellphones are there, either in the

world, or in a region, like a country? So, suppose we had six people?

Would we have, on average, less cellphones than people?

So, we have maybe four cellphones for every six people, meaning that every

person has on average less than one cellphone.

Would we have the same number, meaning that every person's going to have on

average one cellphone? Or would we have more?

Like, eight cellphones for every six people, meaning that every person has on

average more than one cellphone. A decade or two ago there were many, many

more people than there were cellphones, but the number of cellphones has risen

very dramatically in that time. So, these numbers are becoming closer and

closer to one another. At the end of 2012, there were about 7

billion people in the world, and there were about 6 billion mobile

subscriptions. So, we're not actually looking at the

number of manufactured devices, or the number of cellphones that have ever been

made, but we're looking at those that are currently in use or currently subscribe

to a mobile plan. And so, if we looked at the number of

cellphones relative to the number of people, we would have six over seven.

Meaning that for every six phones there are on an average for seven people.

So, this is approaching one, meaning that in the world they're soon going to be on

an average one cellphone per person. So, you may have guessed that number

would have been around one, maybe even a little less than one.

But what you probably didn't know is it's drastically different depends upon which

country you are look at. So, in this graph over here, we're

showing the penetration rate which is this number that we showed down here of

taking the number of mobile subscriptions and dividing it by the number of people

in the population. And this is as of December 2012.

So, if you look at the countries on the right-hand side, over here, you see that

the penetration rates for these countries are less than 100%.

Or, it's just really just this decimal number in percentage form..

And what that means is that there are more peoples than cellphones, that might

make sense because some of these countries have very large populations or

a dense populations. But on the left hand side of this arrow,

these countries have ratios that are over 100%, for instance, United States has

recently gone up to 103%. And that keeps going up more and more

which means that there are actually more cellphones then there are people.

And if we come all the way over here to Russia that is at 160% which means that

there is between one in two cellphones per person and it's closer to the two.

So, there's closer to two cell phones per person than there is one cell phone per

person in Russia. And just to sort of write this out, the

penetration rate is equal to the number of mobile devices.