This summer, I published a book called Bleeding Out that explains how we could reduce gun violence by 50% in the US’s 40 most violent cities. The plan would take eight years and could save more than 12,000 lives. It would cost about $100m a year.

Many people find it hard to believe that we can do a lot with a little on this issue. But urban violence is actually a more solvable problem than most of us realize.

In the cities that struggle with high rates of violence, shootings are concentrated among a surprisingly small set of people and places. It doesn’t concentrate in entire communities or neighborhoods. Even in the most allegedly dangerous places, the vast majority of people are not violent, and there are plenty of safe spaces.

In fact, in most cities, about 4% of city blocks account for approximately 50% of crime. In Oakland, 60% of murders happen within a social network of approximately one to two thousand high-risk individuals – about 0.3% of the city’s population. In New Orleans, a network of 600 to 700 people, less than 1% of the city’s population, account for more than 50% of its lethal encounters.

Conventional wisdom tells us that to address violence, we need to work from the outside in, starting by fixing everything else: culture, poverty, racism, employment. But all of the most rigorous and reliable evidence tells us the opposite: we have to work from the inside out, focusing first and foremost on the highest-risk people and places.

What do we do once we’ve identified who’s most at risk? That’s more complicated. It’s easy to say, “Just get all the guns off the street,” but it’s very hard to do that. It’s easy to say, “Just get everyone a job,” but again that’s hard to actually do. What the evidence shows is that the more effective solutions are actually a bit harder to explain.

I’ve worked on urban violence prevention policy for years, first as a prosecutor in Manhattan, then in Obama’s justice department, and finally for Governor Andrew Cuomo back in New York. What I’ve seen – and what the evidence shows – is that the best strategies to reduce urban gun violence have three things in common: focus, balance and fairness.

In the US, the strategy that has worked the best to reduce urban gun violence is 'focused deterrence'

Effective strategies focus narrowly on the “hot people” or the “hot spots” driving most of the violence. They balance the threat of punishment with prevention, ie real efforts to help even the highest-risk people change their lives without going to prison. And, to be most effective, they need to be perceived as fair – they need to have support and legitimacy within the communities most affected by violence.

In the US, the strategy that has worked the best to reduce urban gun violence is “focused deterrence”, sometimes referred to as the Group Violence Initiative or Ceasefire. It does not work perfectly, and it does not work every time, but it works better, on average, than anything else out there.

The city of Oakland tried this strategy twice, failing each time, before it finally got it right beginning in 2012. They created a partnership between police, prosecutors, key community members and key service providers. Then that partnership identified the individuals and the groups driving ongoing violence in the city. After that, they communicated directly with the highest-risk people through group “call-ins” and “custom notifications”. They let them know that they had been identified as someone likely to shoot or be shot, offered them community support and assistance, and warned them that future violence would be unacceptable and that local law enforcement would come down on them, both individually and as a group, if the shooting didn’t stop. Since 2012, research shows, the strategy has been responsible for cutting homicides almost in half.

Abt’s book discusses strategies to reduce gun violence.

Another notable strategy is “street outreach”, which uses outreach workers with street credibility to intervene with high-risk people and mediate violent disputes before they turn deadly. Often, the outreach workers themselves are formerly incarcerated people or have a history of gang involvement. Los Angeles may have implemented street outreach better than any other city, professionalizing it and making it a central part of the city’s official response to violence. One study showed that between 2014 and 2015, Los Angeles’s outreach program prevented an estimated 185 violent crimes, including 10 homicides.

Cognitive behavioral therapy (CBT) is another strategy that works. It’s a type of therapy that helps make people more aware of their thinking and their decision-making, and helps people practice how to make different choices and build different habits. In one review, CBT was associated with a 25% average decrease in criminal recidivism, and the best programs reduced recidivism by 50% or more. In fact, almost every effective anti-violence prevention program seems to contain, formally or informally, some element of CBT.

We can also use “place-based” strategies to cool down violent hot spots by giving them more police attention and using “cleaning and greening” to clean up trash, repair abandoned buildings and lots, and by planting trees and grass.

So there are multiple treatments for urban violence that are available, affordable and proven to save lives. But they’re still not used in all cities that need them, and they still lack funding and support.

Why? Lack of awareness. Pessimism. Politics.

Urban violence needs to be viewed as a problem to be solved, not an argument to be won. Most of the solutions that have been proven to work challenge, to some extent, the prior ideologies of both sides. There aren’t many effective solutions to urban violence that would appeal entirely to conservatives, or entirely to liberals. Solutions at either end of those political extremes do not have a lot of evidence behind them.

My plan starts with the idea of investing more money in anti-violence programs that have shown evidence of working.

A single homicide can cost anywhere from $10m to $19m. About one-third are direct costs: to the criminal justice system, to the medical system, lost wages for the victim and the perpetrator. The remaining two-thirds are the indirect costs associated with fear and avoidance triggered by homicide – everything from increased insurance premiums to suppressed property values and decreased economic activity.

We all pay those costs. While the impact of urban violence is felt directly by a very small number of people, we are all suffering from it indirectly.

What if we gave cities an additional $30,000 a year for every homicide they saw the previous year, and put that money towards scaling up evidence-based violence prevention efforts?

What if we focused on what can be done over just eight years – so, just two presidential administrations?

Facebook Twitter Pinterest Thousands of activists march onto Chicago Dan Ryan Expressway to protest against violence in the city in July 2018. Photograph: Kamil Krzaczynski/Getty Images

In Chicago, for instance, this would mean investing an additional $112m in violence prevention efforts over eight years, starting with just under $20m the first year.

To scale this up nationwide, include the 20 cities with the highest number of homicides, and the 20 with the highest per capita homicide rates. Investing in these cities at the same funding level would cost about $899m over eight years, with the first year costing $158m.

That is a tiny fraction of our overall national budget, which is almost $4tn a year.

Fully funded and properly implemented, I estimate that the strategies I’ve described could achieve, conservatively, a 10% reduction in homicide every year in the 40 cities with the worst homicide problems.

That would be more than 12,000 homicides prevented. Just in terms of the financial cost to the country, that would be an estimated $120bn saved.

I believe strongly that law enforcement – police, prosecutors, corrections officers – must be part of a balanced solution to reducing urban violence. In the cities that are suffering from urban violence at the highest rates, you often see absolutist discussions, where either police are the entire solution, or police are not to be trusted at all and can’t be a part of the solution. Neither of those extremes are borne out by the evidence. There have to be sticks, but there also have to be carrots.

Chronic exposure to violence is perhaps the single most important factor in addressing concentrated poverty

I also deeply believe in criminal justice reform. But I am not an abolitionist. Poor people of color need an effective criminal justice system that serves them just as well as it does anybody else. We need reconciliation between cops and communities. Between the criminal justice system and those that it has failed to serve in the past.

Reducing the number of homicides in American cities would have profound effects. Chronic exposure to violence is perhaps the single most important factor in addressing concentrated poverty. Just think of the impact that trauma and exposure to violence have on children’s ability to learn and behave and concentrate and even sleep. How that undermines their ability to perform up to their full potential in school, leads to lower incomes down the line and can ultimately trap them in poverty.

The legacy of our ugly history of racial oppression and persecution has resulted in systemic segregation and then disinvestment in certain communities of color. It’s the clustering of disadvantage upon disadvantage over generations that produces this kind of social dysfunction. And that choice has been made collectively, either knowingly or unknowingly, by us all.

As Rabbi Heschel says, few are guilty but all are responsible. Nobody forces someone to pick up a gun and pull the trigger, but we are all collectively responsible for setting up the system we have now, where certain groups of people are pushed towards violence and others aren’t.

There is so much to be done, but my argument is this: focus on violence first. First you stop the bleeding, because unless you stop the bleeding, nothing else matters.