A map showing changes in global homicide rates between 1995-2010. Credit: Cambridge Violence Reduction Centre

New evidence will be presented at the first Global Violence Reduction Conference in Cambridge this week which shows that homicide rates have been declining since the mid-1990s in many parts of the world - in some cases dramatically.

Nations as diverse as Estonia, Hong Kong, South Africa, Poland, and Russia have seen average recorded homicide rates drop by 40% or more in the course of just 15 years. Out of 88 countries where trend data could be found, 67 showed a decline and only 20 showed an increase between 1995 and 2010, a new analysis of data from the United Nations Office on Drugs and Crime has revealed.

The new findings are part of an emerging body of evidence - from research into effective policing strategies, rehabilitation methods, better child protection services, and societal attitude shifts - which has many experts agreeing that global rates of violence could be halved by just 2040 if the right policies can be defined and implemented.

The University of Cambridge and the World Health Organisation (WHO) have brought together 150 of the world's foremost scientists and criminologists to set out the first roadmap for reducing global rates of interpersonal violence - a problem that now causes more death and costs more money than all wars combined.

International support is growing, with the World Health Assembly issuing a resolution for an action plan on interpersonal violence in May this year. Those gathered in Cambridge call on governments and other stakeholders to lobby for violence prevention and reduction to become a concrete part of the UN's post-2015 development agenda.

"Examples of successful homicide reduction over the past 15 years can be found across the world: from Canada and Italy to New Zealand and China. But if we want to achieve a worldwide decline in homicide we need to learn from these success stories and understand what they did right," said Prof Manuel Eisner, conference co-convener and director of Cambridge's Centre for Violence Reduction.

"Evidence from many places in the world suggests reductions in violence by about 2.3% per year - needed for a 50% drop in 30 years - are feasible and realistic." Eisner emphasises that this is not a yet global decline; some countries - primarily Latin American - have seen recent increases in homicide which may offset the overall picture, and little is known about trends in much of Africa. But many European, Northern American and Asian countries are showing a steep decline in homicide over the past two decades, and the lessons from these nations need to be built on.

Eisner's analysis shows that homicide fell in societies that combined improved governance with effective policing strategies, a tighter net of control including surveillance technologies, and a lower tolerance for violent and disruptive behaviour from an earlier age.

The problem of interpersonal violence can seem insurmountable. In the 21st century, homicide has a higher body count than all wars combined - some 8 million people since 2000. Around 30% of women have experienced domestic violence; one in seven children on the planet is thought to be a victim of sexual abuse. Recent research commissioned by the Copenhagen Consensus Centre estimated that domestic violence costs the world $8 trillion annually (more than war).

But many experts feel there is cause for optimism. Interpersonal violence has been steadily declining for hundreds of years; a decline that has become particularly sharp in many societies over the past few decades:

"In London, the risk of being murdered has declined by a staggering 99% from the late Middle Ages to the present day. In the last ten years alone, the number of homicides in London has been cut in half, from around 200 in 2003 to less than 100 in 2013, for example - making it one of the safest cities in the world," said Eisner.

Significant challenges are faced in developing countries, and more research on effective violence reduction needs to be focused on these societies. Almost half (45%) of all homicides worldwide are committed in just 23 countries where only 10% of the world population lives. However, only 5% of all evaluations of effective violence prevention have been conducted outside wealthy western societies.

The causes of violence extend to the institutional backbone of many of these countries. Analysis shows that societies with the highest murder rates in Latin America, Africa and Asia – such as El Salvador, Congo and Russia – suffer from a mix of corruption, highly profitable illegal markets, low investment in public health and education, and an ineffective police force that is not trusted by the citizens.

"Making the state more legitimate in the eyes of its citizens, the police more effective and accountable, and promoting the rule of law will be critical to achieve a significant decline of violence," Eisner said.

Global step-changes are required in the way societies are policed and new technologies are used to prevent violence, say the experts. Currently only 20% of the world's populations live in societies that gather evidence to support better policing; this should increase to 60% by 2044.

"An accountable and effective police that are trusted by civil society is indispensable," said Prof Lawrence Sherman, Director of Cambridge's Institute of Criminology. Sherman, an authority in 'crime experiments', points to a recent example of the role such work could play in violence reduction: an experiment he conducted in Trinidad showed a GPS-mapping strategy for police patrols caused a 41% reduction in murders and shootings.

Most experts agree that violence prevention needs to start earlier in life. Parenting support systems, child protection measures and evidence-based early social skills training hardly exist in areas most affected by child abuse and domestic violence. "We are beginning to see more initiatives in poor countries, where academics, governments and stake-holders find ways to disseminate prevention strategies found to be effective in rich countries," said the conference organisers.

The joint WHO/Cambridge conference will feature latest evidence from a global range of reduction research - from Sao Paulo street gangs to civil conflict in sub-Saharan Africa - and create vital links between violence researchers worldwide with the aim of placing violence reduction on the international agenda.

The WHO's first status report on global violence prevention will be launched this winter, providing a solid information base of where countries stand in prevention efforts, and where the major gaps lie. "This offers an unprecedented opportunity for violence prevention stakeholders to come together and step up their activities," said Alex Butchart, conference co-convener from the WHO.

Eisner calls on governments to develop their own national action plans to reduce violence, and to this end his team will be working closely with the WHO and researchers from every continent to create a series of policy recommendations.