What? How could it possibly?

Here, I'll show you.

Just building a wall would be practically impossible.

This is where it would be.

(dog squeals)

It would have to stretch over 2,000 miles of rough terrain...

cutting through mountains,

rivers, villages

and even people's homes.

And all that destruction is monstrously expensive.

Just building the wall

would cost between $15 and $25 billion.

(woman gasps)

It would easily be one of the single most

expensive pieces of infrastructure

in American history costing as much as 20 Hoover Dams

or NASA's entire annual budget.

(man) That's one small step for man,

one giant wall for no reason.

Not to mention the astronomical cost

of staffing and maintaining the wall,

which taxpayers like you and your children

will be stuck paying forever.

I paid for the wall.

My father's father paid for the wall.

And one day you will pay for the wall.

Because this is Wall World.

Even just faking the wall for our show

was prohibitively expensive.

Looks like our CGI budget ran out.

Okay, yes, it may be expensive

but that doesn't change the fact

that once we build it, it will work.

Not like you think.

Increasing security at the border

will never stop illegal immigration.

Why not?

No one's getting passed me.

Yes, they are because it's estimated that

between 27% and 40% of all undocumented immigrants

in America came here on planes.

(plane passing)

I forgot about planes.

These immigrants didn't sneak over the border.

They came here legally through passport control,

then just overstayed their visas.

And guess what? A border wall's

not gonna stop 'em because, reminder...

You fools!

You forgot about planes!

We always forget about planes!

Even by your estimate of visa overstays,

the wall would still

stop about half

of America's 11 million illegal immigrants.

No, it wouldn't.

'Cause of a little something called circular flow.

Here, I'll show you.

(dog yelps)

For decades, immigration to the U.S. was a circular flow.

People would come,

work for a bit

and then after they were done, go home to their families.

Meet Douglas Massey.

Thanks, Adam.

My arms were getting pretty tired waiting for my cue.

He's a professor at Princeton

and a pioneering researcher on this topic.

When the Reagan, Bush and Clinton administrations

drastically increased border

enforcement in response

to public opinion,

they stopped that circular flow.

Not by keeping people out, but by keeping people in.

(Douglas) As it got harder and harder to go back and forth,

people crossing

the border decided

they were much better off just staying in the U.S.

If I go back to Mexico now,

he won't let me back in the U.S.

I guess I'll just stay here...

in Tucson.

Ironically, this increase

in border enforcement

caused the number of undocumented immigrants

living in the United States to skyrocket by 248%.

It's counterintuitive, but building a wall

wouldn't stop people from coming in.

It would actually stop them from going back.

In fact, the whole idea of

building a border wall

is misguided.

The Mexican economy is doing quite well right now

and population growth has slowed way down.

So, there's not much pressure to emigrate.

The number of illegal border crossings

is actually at an all-time low.

If you're a professor, then why are you in the desert?

I'm not, I'm a mirage.

(gasping) Hey!

Look, humanity discovered vast deposits

of fuel buried deep within the earth.

We learned to extract it, burn it for energy,

and release it into the air,

and about 150 years ago,

we rebuilt our entire civilization

around that energy source.

We burn it to travel, we burn it to eat,

we burn it to live.

Fossil fuels brought about one of the greatest increases

in standard of living in human history.

We could never go back.

But by burning this incredible fuel source,

we are also inexorably heating the earth.

2015 was the hottest year

since we started keeping records in 1880.

And thanks to rising ocean temperatures,

average sea levels have already risen

about eight inches.

And we're in for a lot worse.

This is Dale Jamieson.

He's a professor of Environmental Studies at NYU.

Wayne, we've already done so much damage to the atmosphere

that we'll be lucky if we can hold the warming

to two degrees Celsius.

Two degrees?

Well, that's just the difference

between a jacket and a slightly lighter jacket.

Not to the earth, it isn't.

Just two degrees of warming could cause huge draughts,

massive wildfires, the loss of many species,

the collapse of our agricultural productivity,

and the rising sea levels

could make our coastal cities uninhabitable.

And remember, two degrees of warming

is the best we can realistically hope for.

The question isn't, will warming happen?

The question is, how bad will it be?

That's terrible.

Isn't there something

I can do?

The sad truth is that we've already put

so much carbon dioxide in the atmosphere

that we're more than halfway towards

that two-degree centigrade limit.

And right now, companies and countries already own

enough fossil fuel in reserves

to meet that limit five times over.

Five times over?

To keep it in the ground,

they'd have to give up trillions of dollars

and we'd have to change our entire way of life.

And what happens

if we burn it?

What happens to our planet then?

I don't know, but it won't be our planet anymore.

What happens to our planetible.?

What could be the downside?

Oh, there are a ton.

For starters, how 'bout the fact that this place

rips off folks like you every day.

Whatever.

I know the hospital is expensive,

but it is worth it if I get the best treatment.

No, it isn't.

American health care is not the best in the world.

But despite that, we spend more per person annually

on health care than any other developed nation.

And a big part of the reason for that

is that American hospitals overcharge patients massively.

(music playing, cheering and applause)

This neck brace is worth $20.

But the hospital charged him... $154.

This I.V. bag cost less than a buck.

But she was charged $137.

These are real prices, folks.