by 50 percent in the next three decades.

All we have to do is drop killing by 2.3 percent a year,

and we'll hit that target.

You don't believe me?

Well, the leading epidemiologists and criminologists around the world

seem to think we can, and so do I,

but only if we focus on our cities, especially the most fragile ones.

You see, I've been thinking about this a lot.

For the last 20 years, I've been working

in countries and cities ripped apart by conflict,

violence, terrorism, or some insidious combination of all.

I've tracked gun smugglers from Russia to Somalia,

I've worked with warlords in Afghanistan and the Congo,

I've counted cadavers in Colombia, in Haiti, in Sri Lanka, in Papua New Guinea.

You don't need to be on the front line, though,

to get a sense that our planet is spinning out of control, right?

There's this feeling that international instability is the new normal.

But I want you to take a closer look,

and I think you'll see that the geography of violence is changing,

because it's not so much our nation states that are gripped by conflict and crime

as our cities: Aleppo, Bamako, Caracas, Erbil, Mosul, Tripoli, Salvador.

Violence is migrating to the metropole.

And maybe this is to be expected, right?

After all, most people today, they live in cities, not the countryside.

Just 600 cities, including 30 megacities, account for two thirds of global GDP.

But when it comes to cities,

the conversation is dominated by the North,

that is, North America, Western Europe, Australia and Japan,

where violence is actually at historic lows.

As a result, city enthusiasts, they talk about the triumph of the city,

of the creative classes, and the mayors that will rule the world.

Now, I hope that mayors do one day rule the world,

but, you know, the fact is,

we don't hear any conversation, really, about what is happening in the South.

And by South, I mean Latin America, Africa, Asia,

where violence in some cases is accelerating,

where infrastructure is overstretched,

and where governance is sometimes an aspiration and not a reality.

Now, some diplomats and development experts and specialists,

they talk about 40 to 50 fragile states

that will shape security in the 21st century.

I think it's fragile cities which will define the future of order and disorder.

That's because warfare and humanitarian action

are going to be concentrated in our cities,

and the fight for development,

whether you define that as eradicating poverty,

universal healthcare, beating back climate change,

will be won or lost in the shantytowns, slums and favelas of our cities.

I want to talk to you about four megarisks

that I think will define fragility in our time,

and if we can get to grips with these,

I think we can do something with that lethal violence problem.

So let me start with some good news.

Fact is, we're living in the most peaceful moment in human history.

Steven Pinker and others have shown how the intensity and frequency of conflict

is actually at an all-time low.

Now, Gaza, Syria, Sudan, Ukraine,

as ghastly as these conflicts are, and they are horrific,

they represent a relatively small blip upwards

in a 50-year-long secular decline.

What's more, we're seeing a dramatic reduction in homicide.

Manuel Eisner and others have shown

that for centuries, we've seen this incredible drop in murder,

especially in the West.

Most Northern cities today are 100 times safer than they were just 100 years ago.

These two facts -- the decline in armed conflict and the decline in murder --

are amongst the most extraordinary,

if unheralded, accomplishments of human history,

and we should be really excited, right?

Well, yeah, we should.

There's just one problem: These two scourges are still with us.

You see, 525,000 people -- men, women, boys and girls --

die violently every single year.

Research I've been doing with Keith Krause and others

has shown that between 50,000 and 60,000 people are dying in war zones violently.

The rest, almost 500,000 people, are dying outside of conflict zones.

In other words, 10 times more people are dying outside of war than inside war.

What's more, violence is moving south,

to Latin America and the Caribbean,

to parts of Central and Southern Africa,

and to bits of the Middle East and Central Asia.

Forty of the 50 most dangerous cities in the world

are right here in Latin America,

13 in Brazil,

and the most dangerous of all, it's San Pedro Sula, Honduras' second city,

with a staggering homicide rate of 187 murders per 100,000 people.

That's 23 times the global average.

Now, if violence is re-concentrating geographically,

it's also being reconfigured to the world's new topography,

because when it comes to cities, the world ain't flat,

like Thomas Friedman likes to say.

It's spiky.

The dominance of the city as the primary mode of urban living

is one of the most extraordinary demographic reversals in history,

and it all happened so fast.

You all know the figures, right?

There's 7.3 billion people in the world today;

there will be 9.6 billion by 2050.

But consider this one fact:

In the 1800s, one in 30 people lived in cities,

today it's one in two,

and tomorrow virtually everyone is going to be there.

And this expansion in urbanization is going to be neither even nor equitable.

The vast majority, 90 percent,

will be happening in the South, in cities of the South.

So urban geographers and demographers,

they tell us that it's not necessarily the size or even the density of cities

that predicts violence, no.

Tokyo, with 35 million people,

is one of the largest, and some might say safest, urban metropolises in the world.

No, it's the speed of urbanization that matters.

I call this turbo-urbanization, and it's one of the key drivers of fragility.

When you think about the incredible expansion of these cities,

and you think about turbo-urbanization, think about Karachi.

Karachi was about 500,000 people in 1947, a hustling, bustling city.

Today, it's 21 million people,

and apart from accounting for three quarters of Pakistan's GDP,

it's also one of the most violent cities in South Asia.

Dhaka, Lagos, Kinshasa,

these cities are now 40 times larger than they were in the 1950s.

Now take a look at New York.

The Big Apple, it took 150 years to get to eight million people.

São Paulo, Mexico City, took 15 to reach that same interval.

Now, what do these medium, large, mega-, and hypercities look like?

What is their profile?

Well, for one thing, they're young.

What we're seeing in many of them is the rise of the youth bulge.

Now, this is actually a good news story.

It's a function of reductions in child mortality rates.

But the youth bulge is something we've got to watch.

What it basically means

is the proportion of young people living in our fragile cities

is much larger than those living in our healthier and wealthier ones.

In some fragile cities,

75 percent of the population is under the age of 30.

Think about that: Three in four people are under 30.

It's like Palo Alto on steroids.

Now, if you look at Mogadishu for example,

in Mogadishu the mean age is 16 years old.

Ditto for Dhaka, Dili and Kabul.

And Tokyo? It's 46.

Same for most Western European cities.

Now, it's not just youth that necessarily predicts violence.

That's one factor among many,

but youthfulness combined with unemployment, lack of education,

and -- this is the kicker -- being male, is a deadly proposition.

They're statistically correlated, all those risk factors, with youth,

and they tend to relate to increases in violence.

Now, for those of you who are parents of teenage sons,

you know what I'm talking about, right?

Just imagine your boy without any structure

with those unruly friends of his, out there cavorting about.

Now, take away the parents,

take away the education, limit the education possibilities,

sprinkle in a little bit of drugs, alcohol and guns,

and sit back and watch the fireworks.

The implications are disconcerting.

Right here in Brazil, the life expectancy is 73.6 years.

If you live in Rio, I'm sorry, shave off two right there.

But if you're young, you're uneducated,

you lack employment, you're black, and you're male,

your life expectancy drops to less than 60 years old.

There's a reason why youthfulness and violence are the number one killers

in this country.

Okay, so it's not all doom and gloom in our cities.

After all, cities are hubs of innovation,

dynamism, prosperity, excitement, connectivity.

They're where the smart people gather.

And those young people I just mentioned,

they're more digitally savvy and tech-aware than ever before.

And this explosion, the Internet, and mobile technology,

means that the digital divide separating the North and the South

between countries and within them, is shrinking.

But as we've heard so many times,

these new technologies are dual-edged, right?

Take the case of law enforcement.

Police around the world are starting to use remote sensing and big data

to anticipate crime.

Some cops are able to predict criminal violence before it even happens.

The future crime scenario, it's here today,

and we've got to be careful.

We have to manage the issues of the public safety

against rights to individual privacy.

But it's not just the cops who are innovating.

We've heard extraordinary activities of civil society groups

who are engaging in local and global collective action,

and this is leading to digital protest and real revolution.

But most worrying of all are criminal gangs

who are going online and starting to colonize cyberspace.

In Ciudad Juárez in Mexico, where I've been working,

groups like the Zetas and the Sinaloa cartel

are hijacking social media.

They're using it to recruit, to sell their products,

to coerce, to intimidate and to kill.

Violence is going virtual.

So this is just a partial sketch

of a fast-moving and dynamic and complex situation.

I mean, there are many other megarisks

that are going to define fragility in our time,

not least income inequality,

poverty, climate change, impunity.

But we're facing a stark dilemma

where some cities are going to thrive and drive global growth

and others are going to stumble and pull it backwards.

If we're going to change course, we need to start a conversation.

We can't only focus on those cities that work,

the Singapores, the Kuala Lumpurs,

the Dubais, the Shanghais.

We've got to bring those fragile cities into the conversation.

One way to do this might be to start twinning

our fragile cities with our healthier and wealthier ones,

kickstarting a process of learning and collaboration

and sharing of practices, of what works and what doesn't.

A wonderful example of this is coming from El Salvador and Los Angeles,

where the mayors in San Salvador and Los Angeles are collaborating

on getting ex-gang members to work with current gang members,

offering tutoring, education,

and in the process are helping incubate cease-fires and truces,

and we've seen homicide rates go down in San Salvador,

once the world's most violent city,

by 50 percent.

We can also focus on hot cities, but also hot spots.

Place and location matter fundamentally in shaping violence in our cities.

Did you know that between one and two percent

of street addresses in any fragile city

can predict up to 99 percent of violent crime?

Take the case of São Paulo, where I've been working.

It's gone from being Brazil's most dangerous city to one of its safest,

and it did this by doubling down

on information collection, hot spot mapping, and police reform,

and in the process, it dropped homicide by 70 percent in just over 10 years.

We also got to focus on those hot people.

It's tragic, but being young, unemployed, uneducated, male,

increases the risks of being killed and killing.

We have to break this cycle of violence

and get in there early with our children, our youngest children,

and valorize them, not stigmatize them.

There's wonderful work that's happening that I've been involved with

in Kingston, Jamaica and right here in Rio,

which is putting education, employment, recreation

up front for these high-risk groups,

and as a result, we're seeing violence going down in their communities.

We've also got to make our cities safer, more inclusive, and livable for all.

The fact is, social cohesion matters.

Mobility matters in our cities.

We've got to get away from this model of segregation, exclusion,

and cities with walls.

My favorite example of how to do this comes from Medellín.