The fatal stabbing of a man yesterday in one of London's busiest shopping streets in broad daylight has again thrown up headlines about knife crime in Britain.

Boris Johnson, in accepting the office of London mayor, pledged to rid the capital of the "scourge" of knife crime.

Just hours beforehand, 15-year-old Lylle Tulloch had been stabbed to death in stairwell in Southwark, the 12th teenage fatality in London this year. Since then, 16-year-old Jimmy Mizen was murdered in south-east London, and yesterday a young man in his twenties was knifed outside a McDonalds in Oxford Street.

Incidents such as these have fuelled the public perception that knife crime is out of control, yet this is not borne out by the statistics.

According to the British Crime Survey, knife-enabled crime (any crime involving a knife) over the past decade has remained stable at around 6-7% of all crime, comprising 30% of all homicides.

In fact, the most recent crime survey by the Metropolitan police showed that knife crime has actually dropped by 15.7% over the past two years, from 12,122 to 10,220 incidents.

Nevertheless, that still amounts to a knife-related incident every 52 minutes. Knife crimes were also four times more prevalent than gun crimes; and the risk of serious injury was more than double than that for gun crime – statistics that will give the London mayor and his newly appointed knife tsar, Ray Lewis, pause for thought.

Concern over stabbings is not limited to the capital, however. The prevalence of knives on the streets has increased in recent years, according to the Police Federation of England and Wales which will be discussing knife crime and gang violence at the organisation's annual conference next week.

Knife crime affects young people disproportionately. Statistics show that teenagers in London, particularly those between the ages of 17 and 20, are the most likely to be victims of knife crime, according to the Metropolitan police.

Also notable is the increase in violent crimes committed by 15 and 16-year-olds. According a survey compiled by the Youth Justice Board (YJB), violent offences committed by 16-year-olds rose from 17% in 2004, to 25% in 2005, while those perpetrated by 15-year-olds climbed from 20% in 2004, to 26% in 2005.

Related to this is the increased number of young people arming themselves with knives. The YJB survey reported a 12% increase in the number of teenagers carrying knives since 2002, with the proportion of girls carrying knives rising sharply in recent years, from 15% in 2004 to 21% in 2005.

One in five of those convicted for possessing a knife were aged between 10 and 17 in 2006, according to Home Office statistics.

In their report, the YJB asserted that the increase in children carrying knives was primarily out of fear of bullying or attack, the perception that all their peers carry knives, or to gain "street cred".

"There is an overlap between teenagers who carry weapons and those who have been victims of knife crime," Enver Solomon, deputy director of the Centre for Crime and Justice Studies told the Guardian.

"If someone has been a victim of crime, they might carry a weapon because they feel unsafe. They don't inherently want to stab someone; it's just that the knife in the pocket makes them feel secure. The majority of children are carrying pen-knives, not machetes," he said.

Simply clamping down on the supply of knives – such as the installation of metal detectors at schools or equipping police with mobile metal detectors, as Mayor Johnson recently suggested – is not sufficient to address the problem, he added.

Instead, the mayor should focus on the social conditions in a cluster of boroughs that have generated a disproportionate number of the capital's knife crimes. Quoting Metropolitan police studies, Solomon said 2% of London wards have been responsible for 10% of all violent crimes involving teenagers.

"If you examine the conditions in these wards, these are areas of high social deprivation, social exclusion and lack of opportunities for young people," he explained. "The focus should not be on enforcement, but rather on opportunities for kids, through youth support services, peer mentoring schemes and employment opportunities for school-leavers."

Home Office measures to tackle knife crime have included an amnesty in 2006, which resulted in almost 100,000 knives being handed in, the doubling of the maximum penalty for possession of a knife from two to four years' imprisonment, giving teachers new powers to search students for weapons, raising the minimum age for knife ownership to 18 and, most recently, imposing a ban on samurai swords.

But focusing on deterrence is inadequate, said Solomon, adding that the key to reducing knife crime was creating a safer environment for youngsters as well as increasing opportunities for young school leavers.

"You have to look at the social drivers. Why do young boys slip into the illegal drugs economy? It's not a positive choice, but for some of them it seems to be the only choice. You have to use a range of policy levers to tackle this problem."