In West Side Story Stephen Sondheim set out the theories of juvenile delinquency with more clarity, and certainly more brevity, than the academics who had dreamed them up. A prominent theory in sociological circles is that crime arises from poverty and consequently that the alleviation of poverty by paying social benefits should diminish criminality.
The link between poverty and crime has been demonstrated repeatedly, and recently confirmed for USA and Norway. Repetition of a correlation impacts academic and public opinion. However, as we are wearily cognizant of, correlation is not causation, though in ordinary life it damn well implies it. Correlation is a necessary feature of causation, but not a sufficient proof. The quip should be altered to: correlation is not always causation, but it helps.
This link has been investigated, in a different way, by a gang of sociologists led by Amir Sariaslan (ex-Uppsala) and his colleagues at the great Karolinska in Sweden, the country of Volvo, Saab (RIP), Bofors guns, Primus stoves, interminable Bergman movies, winter candles on the streets of gamla gatan, pacificism, social welfare, and obsessional scandinavian epidemiology. The latter has proved a redeeming feature.Childhood family income, adolescent violent criminality and substance misuse:
quasi-experimental total population study. Amir Sariaslan, Henrik Larsson, Brian D’Onofrio, Niklas Langstrom and Paul Lichtenstein. British Journal of Psychiatry.
Published online ahead of print August 21, 2014, doi:10.1192/bjp.bp.113.136200
Children of parents in the lowest income quintile experienced a seven-fold increased hazard rate (HR) of being convicted of violent criminality compared with peers in the highest quintile (HR = 6.78, 95% CI 6.23–7.38). This association was entirely accounted for by unobserved familial risk factors (HR = 0.95, 95% CI 0.44–2.03). Similar pattern of effects was found for substance misuse.
The authors point out:
Behavioural genetic investigations have found that the liabilities for both violent offending and substance misuse are substantially influenced by shared genetic and, to a lesser extent, family environmental factors.7,8
7 Frisell T, Lichtenstein P, Langstrom N. Violent crime runs in families: a total
population study of 12.5 million individuals. Psychol Med 2011; 41: 97–105.
8 Kendler KS, Sundquist K, Ohlsson H, Palme r K, Maes H, Winkleby MA, et al.
Genetic and familial environmental influences on the risk for drug abuse:
a national Swedish adoption study. Arch Gen Psychiatry 2012; 69: 690–7.
We linked data from nine Swedish, longitudinal, total-population registers maintained by governmental agencies. The linkage was possible through the unique 10-digit civic registration number assigned to all Swedish citizens at birth and to immigrants upon arrival to the country.
The final sample (omitting multiple-births, death, severe handicap and emigrants) consisted of 88.6% of the targeted population (n = 526 167). The
sample included 262 267 cousins and 216 424 siblings nested within 114 671 extended and 105 470 nuclear families.
We calculated mean disposable family income (net sum of wage earnings, welfare and retirement benefits, etc.) of both biological parents for each offspring and year between 1990 and 2008. Income measures were inflation-adjusted to 1990 values according to the consumer price index provided by Statistics Sweden.
Gender, birth year and birth order were included in all models. We also adjusted for highest parental education and parental ages at the time of the first-born child, and parental history of ever being admitted to hospital for a mental disorder.
Violent crime was defined as a conviction for homicide, assault, robbery, threats and violence against an officer, gross violation of a person’s/woman’s integrity, unlawful threats, unlawful coercion, kidnapping, illegal confinement, arson, intimidation,
or sexual offences (rape, indecent assault, indecent exposure or child molestation, but excluding prostitution, hiring of prostitutes or possession of child pornography).
The participants entered the study at their fifteenth birthday and were subsequently followed up for a median time of 3.5 years. The maximum follow-up time was 6 years.
This is a short time to pick up the full flowering of criminal careers, so perhaps should be considered and under-estimate, or purely a measure of juvenile delinquency and not of life time criminality (which usually lasts until middle age).
Readers will know that I cast a particularly baleful eye over all “corrections” and “adjustments” but in this paper the techniques are transparent, and have an intrinsic justification. The data allows them to compare siblings with cousins, and intact nuclear families with more scattered ones: two natural experiments which allow contrasts of shared genes and experience. Crafty. That is my summary, but here is their explanation in detail:
We fitted two separate models for the entire sample (n = 526 167) that gradually adjusted for observed confounding variables. Model I adjusted for gender, birth year and birth order, whereas Model II also adjusted for highest parental education, parental ages at the time of the first-born child and parental history of admission to hospital for a mental disorder.
To assess the effects also of unobserved genetic and environmental factors, we fitted stratified Cox regression models to cousin (n = 262 267) and sibling (n = 216 424) samples with extended or nuclear family as stratum, respectively. The stratified
models allow for the estimation of heterogeneous baseline hazard rates across families and thus capture unobserved familial factors. This also implies that exposure comparisons are made within families. Model III was fitted to the cousin sample and adjusted for observed confounders and unobserved within extended-family factors. Model IV was fitted on the sibling sample and accounted for unobserved nuclear family factors and for gender, birth year and birth order.
Cousin and sibling correlations on the exposure variable were calculated based on a varying-intercepts, mixed-effects model where the intercepts are allowed to vary across families.
The magnitude of the variation was expressed as an intra-class correlation (ICC). The ICC measures the degree to which observations are similar to one another within clusters; in this case cousins and siblings nested within extended and nuclear family clusters. The measure ranges between 0 and 1, where the latter implies that cousins and siblings have identical exposure values within families.
As you can see, each model picks away at what would otherwise be seen as a purely economic cause of criminality and drug abuse. Model II which adjusts for parental education and mental illness has a big effect.
In an unusual departure, The Economist devoted an article to this paper, which suggests that they are beginning to wake up to the human factors in economics. Admittedly, they sub-titled it A disturbing study of the link between incomes and criminal behaviour, suggesting they were disturbed. Here are The Economist’s conclusions:
That suggests two, not mutually exclusive, possibilities. One is that a family’s culture, once established, is “sticky”—that you can, to put it crudely, take the kid out of the neighbourhood, but not the neighbourhood out of the kid. Given, for example, children’s propensity to emulate elder siblings whom they admire, that sounds perfectly plausible. The other possibility is that genes which predispose to criminal behaviour (several studies suggest such genes exist) are more common at the bottom of society than at the top, perhaps because the lack of impulse-control they engender also tends to reduce someone’s earning capacity.
Neither of these conclusions is likely to be welcome to social reformers. The first suggests that merely topping up people’s incomes, though it may well be a good idea for other reasons, will not by itself address questions of bad behaviour. The second raises the possibility that the problem of intergenerational poverty may be self-reinforcing, particularly in rich countries like Sweden where the winnowing effects of education and the need for high levels of skill in many jobs will favour those who can control their behaviour, and not those who rely on too many chemical crutches to get them through the day.
This is only one study, of course. Such conclusions will need to be tested by others. But if they are confirmed, the fact that they are uncomfortable will be no excuse for ignoring them.
What The Economist might have said is: Since this is a total population study of five birth cohorts and is the largest by far in the literature, it has high credibility, and the result will stand until another study of equal quality finds otherwise.