An intruder is stabbed to death during a burglary in London’s Hither Green. Across town in Hackney, two men are killed by stabbing. The killings sent London’s 2018 death tally to 50, up by a half on the same period last year. Britain is facing a “murder crisis”. Or is it facing a crisis in the journalism – and politics – of statistics?

Personal tragedies are hard not to report. Carnage on the streets of London is a story. If it bleeds it leads, especially if bolstered by a usable, and abusable, fact. London’s recent killings generated a sensational one. For the first time in living memory, its murder rate overtook New York’s, with 22 deaths in March to the Big Apple’s 21. Those of us who were once smug about America’s urban violence had a rude shock. Was Harlem to be upstaged by the killing fields of Hackney?

But comparing murder rates for periods of less than a year is dumb. On a more sensible annual basis, 290 New Yorkers were murdered last year, more than double the 116 Londoners. America’s “intentional killing” rate is 4.8 per 100,000 inhabitants, Britain’s is 0.9. Even within Europe, Britain is far better than eastern Europe, and better than France, Sweden and even peaceable Denmark. It is marginally worse than Germany, Italy and Spain. As for London, its murder rate had been steadily falling since the 1990s. It rose in the 2000s, fell during the recession, and is still a quarter lower than it was just a decade ago. It is not “in crisis”.

Yet something is clearly wrong when a spate of “reported incidents” has delivered an annual rise of 20% in both gun and knife attacks in England and Wales. Often a surge in recorded crime tends to reflect police activity – “drug crimes” record police swoops – but murder rates are real. Even the normally calm Office for National Statistics says: “While it is possible that improved recording and proactive policing has contributed to this rise, it is our judgment that there has also been a genuine rise.” The problem seems largely confined to London.

The Metropolitan police are predictably under intense pressure, leading to the usual solutions-fest. The most obvious come from the police themselves, inspiring headlines such as “knife and gun crime rockets … as police numbers hit historic lows”. No one mentions the fact that murders were higher when police numbers were too. The government, the courts and London’s police chief, Cressida Dick, are ordered to arrest more people, toughen penalties and return to aggressive stop and search. Dick can only plead, and rightly so, for someone to curb the killers’ exploitation of social media.

Mary Tuck saw urban crime as reflecting demographics, age groups and the urban culture of cities like New York

Half the killings are said to be gang-related and many of the rest are the work of the drugs market. Both seem resistant to judicial deterrence. But then no area of public policy is so immune to evidence-based research as crime. This is because policymakers pay more attention to the press than to facts. They believe that because the police are there to stop crime, if it rises it must be their fault.

New York’s shift from being one of the worst American cities for security to being the best over the past two decades is endlessly cited. This “followed” the zero-tolerance policing of Bill Bratton, New York’s police chief in the 1990s. The period has been studied to destruction. The wisest expert on comparative murder rates was the Home Office’s research chief at the time, Mary Tuck. She was sceptical of what police could achieve. She saw urban crime as reflecting demographics, age groups and the urban culture of cities such as New York, with high levels of poverty associated with illegal immigrants forced to live outside the law.

Tuck predicted that New York’s then dreadful crime rate would fall when newcomers settled down and accepted domestic patterns of group behaviour – witness the decline of the mafia. They would move out of illegal employment, especially drugs. The murder rate would also improve if New York did something about its dire hospital trauma service. All this came to pass. The city’s violent crime rate has halved since the 1990s.

Study after study from New York’s Brennan Center for Justice has found no causal relationship between urban crime and incarceration, sentencing or police numbers. The anti-gun lobby might note that nor is there a relation between gun crime and local gun controls. Crime appears to be a function not of official policy, but of social conditions.

Experience suggests that London’s present surge in violence will subside. Nothing would do more to speed the process than drug decriminalisation. Britain’s drug laws are the Home Office’s uniquely potent gift to London’s criminal community. They are a Whitehall subsidy to the gangs.

It may be disappointing for the get-tough lobby to be told that policing can have little impact on crime. But even if crime is a function of demography, the police can at least supply reassurance. When I walked the “no tolerance” streets of Manhattan in the Bratton era, immediately noticeable was the presence of single officers on street corners, not in groups or cars. People unquestionably felt more secure as a result.

Today you can walk the troubled streets of Kilburn and Hackney and see no officers. All you hear are the distant, unsettling wails of police-car sirens. Beat police are the “eyes and ears” of a neighbourhood. They are its linking sinews. The only place in London where you still find police patrolling the streets by the dozen is round Parliament Square and Buckingham Palace. I wonder why.

• Simon Jenkins is a Guardian columnist