>> Move us all, thank you.

Cool, so you guys this is awesome,

I've been watching the lectures in this course,

isn't it absolutely amazing the content?

And now you're stuck with me today.

>> We'll, so how that goes.

Unlike Paul, when he was talking in the Q and A,

and you guys asked him what he would do if he was at

college today and

he said physics, I actually indulged myself.

I went in, I went and did physics,

did physics at Cambridge and I think physics is

an amazing class to give you transferable skills that

are really useful in other areas.

But I guess that's not,

that's not why you're listening to me today.

Like, physics isn't the class, like, so I paid for

college doing online marketing.

Direct sales marketing.

I started with SEO in the 1990s.

I created a paper airplane site.

I had a monopoly.

In the small niche market of

paper airplanes globally which you know,

when you want to start a startup also see how big

the market could be in the long term it wasn't great.

But what that taught me was how to do SEO.

And back in those days it was Altavista, and

the way to do SEO was to have white text on

a white background five pages below the fold.

And you would rank top of Alta Vista if you just paper

airplanes 20 or 30 times in that text.

And that was how you won at SEO in the 1990s.

Like it was a really easy, easy skill to learn.

When I went to college, being a physicist,

I thought paper airplanes would make me cool, and

I was actually the most nerdy person in

the physics class, so I created a cocktail site.

Which was how I learned to program.

And that grew to be the largest cocktail site in

the UK.

And that really got me into SEO properly when

Google launched.

So with Google, you had to worry about page rank, and

you had to worry about getting links

back to your site.

Which basically, at that stage,

meant one link from the Yahoo directory.

Got you to the top listing in Google if you had white

text, on a white background, below the fold, as well.

When Google launched AdWords that's when I

really started to learn how to do all my marketing.

And that was buying paid clicks from Google, and

reselling them to eBay for

a small margin of like 20% using our affiliate program.

And that was what really kicked me into overdrive

into doing what everyone nowadays talks about is

growth, or growth hacking, or growth marketing.

And in my mind it's just internet marketing.

Using whatever channel you

can to get whatever output you want.

And that's how I paid for college and how I

ended up going from being a physicist to a marketer and

transitioning to the dark side of the force.

So what do you think matters most for growth.

You've had loads of lectures and

people have said it over and over, so

what do you guys think matters most for growth?

Someone give me an answer.

>> Great product.

>> Great product.

I agree, great product.

What does great product lead to?

>> Customers.

>> Customers.

And what do you need those customers to do?

>> Spread the word.

Someone said stay on your site.

Someone said that.

That's it. Retention.

Retention is the single most important thing for growth.

Now we have an awesome growth team at Facebook, and

I'm super proud to work on it.

But the truth of

the matter is we have a fantastic product.

But getting to work on growth at Facebook is

a massive privilege, because we're promoting something

that everyone in the world really wants to use.

Which is absolutely incredible.

If we can get people on, and

get them ramped up, they stick on Facebook.

So many times I go advise multiple startups,

my favorite was working with Airbnb, but

I've worked with Coursera, I've worked with

other ones that haven't done as well as those guys.

But the one thing that is true over, and over, and

over again is if you look at this curve.

The sentiment, the active,

versus number of days from acquisition.

If you end up with a retention curve that

ascentotes to a line parallel to the x axis.

You have a viable business, and

you have product market fit for some subset of market.

But most of the companies that you see fly up,

we talk about growth hacking and virality and

all of this other stuff.

I'm gonna try so hard not to swear, but it'll happen.

Their attention curve slopes down towards the X-axis, and

in the end intercepts the X-axis.

Now when I show this chart to

most people they say that's all well and good.

You had a million people a day in terms of

growth when you started the growth team at Facebook, or

you were at 50 million users.

You had a lot of people joining the site so

you had a ton of data to do this.

We used this same methodology for

our B to B growth.

Getting people to sign up as self-service advertisers,

we used this analysis to understand how much

growth we were gonna have in that market as well.

And in that place,

when I joined Facebook, the product was three days old.

And within 90 days of the product launching,

we were able to use this technique to be able to

figure out what the one year value of an advertiser was,

and we predicted it for the first year to 97% of

what the number turned out to be.

So I think it's very important to look at

your attention curve, and this is how we did it.

If you see here.

This red line is number of users,

who have been on your product for

a certain number of days.

So, a bunch of people, that should say zero,

a bunch of people will have been on your product,

all of your users will have been on it at least one day.

But, if your product's been around a year, or whatever,

you will have zero users who've been on it 366 days.

Make sense?

The curves sensible?

Cool.

So what you then do is look for all of your users,

who have been on your product one day.

What percentage of them are monthly active.

100% for the first 30 days obviously,

because monthly active they all signed up on one day.

But then you look at 31.

Every single user, on their 31st day after registration,

what percentage of them were monthly active, 32nd day,

33rd day, 34th day?

And that allows you,

with only something like 10,000 customers or

whatever, to get a real idea of what this curve is

gonna look like for your product.

And you're gonna be able to tell does it asymptote.

And it'll get noisy out towards the right-hand side.

Like I'm not using real data.

It'll get noisy out towards the right hand side, but

you'll be able to get a handle on,

does this curve flatten out or does it not.

If it doesn't flatten out, don't go and

do growth tactics, don't go and

do virality, don't hire a growth hacker.

Focus on getting product market fit.

Because in the end,

as Sam said in the beginning of this course,

idea, product, team, execution.

If you don't have a great product,

there's no point executing well on growing it.

Because it won't grow.

Number one problem I've seen inside Facebook for

new products, number one problem I've seen for

startups I ever devised has been, they don't actually

have product market fit when they think they do.

So the next obvious question that people ask over and

over and over again is okay, so

what does good retention look like?

Sure I can have five percent retention but

I'm guessing that Facebook had better than that, so

that's not gonna be a successful business.

And I get really pissed off when

people ask me that question.

Because I think you can figure it out.

And I love this story, and this is like my one

gratuitous story that I love that I'm throwing in here,

so the rest of it may not be as gratuitous.

But this is a picture that was published in

Life magazine in 1950 of

one of the Trinity nuclear bomb tests.

And there's a guy,

Geoffrey Taylor, who's heard of Geoffrey Taylor.

Awesome.

Yes.

Someone's heard of him.

Geoffrey Taylor was a British physicist,

who ended up actually winning the Nobel Prize.

And he was able to figure out from looking at

this picture, what the power of the atomic bomb was,

the U.S. atomic bomb.

And Russian's were publishing similar pictures,

just using dimensional reasoning.

And dimensional reasoning is I think,

one of the best skills that I learned during my

time studying physics back in the U.K..

And what dimensional reasoning is, is you look at

the dimensions that are involved in a problem.

So, you wanna figure out energy?

Newtons, meters, newtons are kilograms, meters are second

to the minus 2, so you've got kilograms,

meters squared, seconds to the minus 2,

and then you try and figure out how you can get each of

those numbers from what data you have.

So, the mass.

Is the volume of this sphere.

So, that's a meter cubed you throw in there.

So you've got meters the 5 over seconds the minus 2,

and he was able to use that to just figure out

what the power of this atomic bomb was,

what the ratios of the power between the Russian and

US atomic bomb, and essentially reveal one of

the top secrets that existed in the world at that time.

That's a hard problem.

Figuring out what

Facebook's retention rate is not a hard problem.

How many people are there on the internet?

Give or take someone throw something out.

>> 2.4 billion, 2.3 billion.

Something like that right?

Okay, Facebook's banned in China.

So.

What now?

>> About a billion.

>> About 2 billion?

2 billion. So

2 billion people on the internet.

Facebook in their last earnings call

said something around 1.3 billion in

terms of the number of active users.

You can divide those numbers by each other.

And yeah, that won't give you the right answer.

Course it's not gonna give you the right answer.

But it's gonna give you

close enough to a ballpark figure.

Of what the retention rate looks like for Facebook.

If we signed everyone on the internet up, and

then you will know it is higher than that.

Similarly if you look at Whats App, they've announced

six hundred million active users.

How many people have smart phones?