On the south side of Northampton, a town an hour's drive north of London, stands a former cinema that is now the home of a discount sofa warehouse called The Sofa King. Outside, a sign proclaims the prices to be "Sofa King low!" Inside, Mark Kypta, a savvy former estate agent, produces a business card that introduces him not as the proprietor, but as The King.

Kypta knows the town well: he was raised there, his parents live there; he knows where the business opportunities lie and which neighbourhoods are best avoided after dark. Asked whether he believes crime to be going up or down in Northampton, his response is immediate: "Up – it's got to be hasn't it?" And nationwide? "It's going up!"

Kypta is far from alone. At the other end of the road is The Bop Shop, a rock'n'roll memorabilia store run by Johnny Dowling. Asked about criminality in Northampton, Dowling, an ageing rocker who has lived in the town for 35 years, reels off his own unhappy experiences: his wife held at gunpoint while working at a petrol station – "he got 10 years for that"; the woman who burst into his shop, squirted petrol at him and threatened to set him alight – "the police showed me mugshots of skinny women with lank hair, all junkies: you couldn't tell one from another"; the man who tried to kick his front door down one Christmas: "I slipped the latch, he fell inside, and I was waiting with a length of three-by-four – bang!" Dowling pauses. "Allegedly," he adds, "you'd better say allegedly waiting …"

All over town, the story is almost invariably the same. Crime is probably going up across Britain, people say, and it's most certainly going up in Northampton.

Except that it is not. According to the official statistics, crime is falling across Britain. It has been falling steadily for almost 20 years, despite the occasional spike in the statistics for some forms of crime. And over the past 12 months, the sharpest fall – 19% – has been recorded in Northampton.

But it is not just the people of Northampton who are perplexed by crime trends. Surveys have shown that while most people in England and Wales believe lawlessness to be falling in the area where they live, the overwhelming majority believe it to be rising nationally, when it has actually fallen to its lowest level in decades. The Office for National Statistics (ONS) believes this may be explained by the way some crimes are reported in the media.

The experts are just as baffled as the public: like the economists who failed to foresee the global financial crisis, criminologists were taken by surprise by what happened during the years of recession that followed the crash. Public spending was cut, unemployment rose, incomes were squeezed, families resorted to food banks. And yet, against all expectations, the number of recorded offences fell.

This phenomenon is not unique to Britain: crime has been falling steadily across much of the western world.

But while most senior police officers, social scientists and Home Office officials accept that crime is falling across Britain, they rarely agree on the cause. Some highly respected criminologists believe so-called acquisitive crime must have risen during the recession, and argue that the surveys are asking the wrong questions: that new forms of crime – often perpetrated online – are not being acknowledged.

Crime in Britain, and the way it is viewed, has become a preconception wrapped in a myth inside a conundrum.

Survey



There are two ways of assessing crime in Britain. The police keep records of the crimes reported to them and, since 1982, a survey of 35,000 households, nowadays known as the Crime Survey for England and Wales (CSEW), records the public's experience of crime. A separate survey of 12,000 households records Scottish crime.

Police chiefs complained for years that Home Office changes to the way they were expected to record crime rendered their figures next to useless for anyone searching for trends. Earlier this year they suffered the humiliation of seeing the UK Statistics Authority withdraw the gold-standard status from crime data that the police record, after the Commons public administration select committee heard evidence that a number of forces had for years been under-recording crime, particularly sexual offences, in an attempt to meet national targets.

There are acknowledged problems with the CSEW too: it leaves out crimes committed against businesses, such as shoplifting, and does not question some of the most vulnerable people – such as the homeless – who may be victimised repeatedly. It has always recorded greater levels of crime than the police figures, however, and has long been regarded as more reliable.

Both sets of figures showed crime to be rising sharply across Britain during the early 1980s, at a time when unemployment was soaring. So too was the use of heroin. The drug was being smuggled into the country from Pakistan and Iran in increasing quantities, its use spreading from a relatively small number of middle-class people in London to the deprived areas of the cities of northern England and Scotland.

"By 1984, the hotspots were Edinburgh, Glasgow, Merseyside, Greater Manchester and parts of London," says Prof Howard Parker, who ran more than 30 drug research projects over more than two decades. "A little later heroin reached Torquay and other parts of the south-west. It was less common in some areas and barely touched Northern Ireland, but that was basically down to the IRA."

The waves of burglaries and car crime were frequently attributed to addicts – and no doubt some government ministers of the day were relieved to be able to blame lawlessness on individual moral fecklessness, rather than on their own policies – but this became increasingly difficult towards the end of the decade as sophisticated statistical analyses demonstrated that economic conditions appeared to be driving crime trends.

One particularly influential report in 1990 [pdf], based on the work of a Home Office researcher, showed that whenever the British economy had been weak over the previous 45 years, and money tight, there had been a rise in property crime, such as theft. Times of relative plenty, on the other hand, saw an increase in personal crime, such as sexual offences and violence – but not robbery – as people consumed more alcohol, particularly beer, and spent more time outside their homes.

There are other theories put forward to explain the rise and fall of crime. Opportunity and security theories suggest acquisitive crime rises when such offences become easy to commit, and falls when they become more difficult. So, theft from cars increased in the 1970s when manufacturers began to install radios; the theft of cars increased because there were more cars on the roads; and the increase in female employment was said to explain a rise in burglary, because more homes were empty during the day. Conversely, falls in such crime may be explained by improved locks and immobilisers, enhanced home security, and CCTV.

The criminal justice theories suggest that crime trends can be driven by the number of offenders held behind bars and the length of their sentences, and by police numbers, resources and strategies. As a result, there were dire warnings in 2010 from the Police Federation, which represents rank and file police officers in England and Wales, that planned cuts in the policing budget would result in "Christmas for criminals".

Theories

Then there are the offender-based theories, which argue that the nature of offending shifts according to changes in the stock of would-be criminals. There have been studies [pdf] on the impact on crime of the legalisation of abortion, for example, and others [pdf] examining the introduction of lead to petrol and its subsequent removal, and the effect that this had on the development of children's brains.

There are problems with each of these sets of theories. The opportunity and security theories fail to explain why burglaries and car crime not only rose in tandem but also fell together, along with violent crime; the criminal justice theories do not help us understand why crime came down in Germany and the Netherlands after those countries reduced their prison populations, nor why offending rates fell when policing numbers were cut – Christmas never came for criminals.

The economic theory held up well for decades, however; so well that in early 2009, as the recession deepened, Chris Grayling, now the justice secretary but then the shadow home secretary, claimed that the Labour government was incapable of getting to grips with what he termed the "credit crunch crime wave", while Chris Huhne, then the Liberal Democrats' home affairs spokesman – who later served time in jail for perverting the course of justice – declared: "There is now clear evidence of rising crime as the recession bites." In fact, crime continued to fall, as it had done since 1995. It appeared to be time to lock up the economic theory and throw away the key.

In July, the Home Office appeared to have come full circle when it published a research paper that suggested the heroin epidemics of the early 80s and early 90s may have fuelled the rise in acquisitive crime, and that the 19-year fall in crime across England and Wales could be explained by the fall in drug use.

After comparing statistics showing the spread of heroin use around the country with local and national statistics about acquisitive crime – and by examining similar data from Ireland and the US – the author reasoned that the study of geographic variations in crime and drug use "offers the best chance of unlocking the crime-drop puzzle". He concluded that crimes committed by heroin and crack cocaine users could account for at least half of the crime rise from the early 80s until 2005, and for between a quarter and a third of the subsequent fall, to 2012, as drug users quit or died.

While stressing that a combination of different factors might explain crime trends, to different degrees at different times, the report also concludes that "preventing a future epidemic is crucial" if crime levels are to remain low.

Addiction



Heroin use was linked to the rise in crime in the 1980s. Photograph: Julian Simmonds/Rex Features

Parker believes the report to have accurately reflected the role that drugs and addiction played in fuelling crime in Britain, and says more work should be done to prevent a future epidemic.

However, some criminologists remain convinced that drug use can provide only a partial explanation for the steady rise in crime, and for its unwavering decline.

Prof Mike Hough, associate director of the Institute for Criminal Policy Research at Birkbeck, University of London, says that rather than searching for narrow explanations for falling crime, people should consider a more general cultural cause: "There is a very long-run trend in European cultures towards greater civility and better treatment of our fellows, however naively optimistic that may seem. If one takes a long view – over centuries – it is pretty obvious that this is the case."

Hough believes societies are reverting to this long-term trend as a result of a combination of reduced opportunities for criminals, better policing, reduced drug taking and, to a small extent, increased use of imprisonment, and that it is the swings around this trend that need explaining.

Other criminologists question whether the two main sources of the official statistics tell the full story, and whether they adequately reflect the enormous recent changes in society.

Some statistics are beyond dispute: the figures that place Britain's murder rate at its lowest level for decades must be correct, as they rely largely on the number of victims' bodies. The reasons for the fall in the number of murders and other violent crime remain elusive, however, with researchers pointing to reduced alcohol consumption, improved treatment of some mental health problems and higher incarceration rates as possible answers.

Other figures are disputed: Marian FitzGerald, visiting professor of criminology at the University of Kent, says the CSEW fails to adequately assess credit card fraud, which is usually reported to the card issuer but not to the police.

FitzGerald also believes the survey takes too little account of the way in which crime has moved online. The survey asks questions about cybercrime, but the ONS has yet to decide whether to include the answers in the main set of results. The internet, FitzGerald says, offers a low-risk opportunity for piracy, fraud and the sale of stolen or counterfeit goods, as well as for blackmail and harassment. "As yet, the crime survey has not asked about the range of victimisation its respondents may now be experiencing via these media, rather than in physical space," she says.

John Graham, director of the Police Foundation thinktank, agrees. "I think crime probably did go up during the recession, but wasn't reflected in the crime figures," he says. "There has been a shift in the way crime is happening. Much of it is moving online, organised crime is difficult to assess, and the amount of money that is made through fraud is greater than the money made through drugs, but we have never been good at counting fraud."

In 2012, the Serious Organised Crime Agency warned MPs on the Commons home affairs select committee that the internet had allowed criminals to commit some traditional crimes on "an industrial scale", leading the committee to conclude [pdf] that what it describes as low-level e-crime is being committed on a vast scale, and with impunity.

In addition to traditional crime that may be facilitated by the internet, there is a generation of new crimes, such as music piracy, phishing, cyberbullying and denial of service attacks, that would not have been possible a few years ago. While police and prosecutors have moved rapidly to deal with some emerging online offences – such as the use of the internet to to incite Islamist terrorist attacks – their initial response to phone hacking showed them to be reluctant to devote resources to other contemporary digital crimes.

If FitzGerald and Graham are correct and new forms of crime are either not being reported to police or not recorded by them – and are also overlooked by the crime surveys – then the curious case of Britain's vanishing crime wave appears to be an even more difficult case to crack.