といえば複雑な環境に育った女性主人公の活躍を描いたベストセラーだが、その小説が生まれたスウェーデンで、養育環境が大人になった時の犯罪傾向に与える影響を調べた研究がなされている（Economic Logic経由）。
以下はその要旨。
We estimate the average treatment effect on the treated of out-of-home care during childhood on adult criminality. In contrast to previous studies on out-of-home care, we look separately at the effects of foster care and residential care and allow these effects to vary by gender and by age at initial placement. We find that foster care has an adverse effect on the adult criminality of boys first placed during adolescence (age 13-18), but no effect for boys who were placed before age 13. Foster care has no effect on the adult criminality of girls. Both boys and girls who were first placed in residential care during their adolescence have higher adult criminality than their never-placed counterparts. We find no such effects for those placed before age 13.
（拙訳）
我々は、子供時代に家庭から離れて育てられたことが成年後の犯罪に与える平均的な影響を推計した。家庭外養育に関するこれまでの研究とは違い、我々は里親による養育と施設での養育を分けて扱い、性別と最初に家庭外に置かれた年齢による違いも調べた。その結果、思春期（13-18歳）に家庭外に最初に置かれた少年の成年後の犯罪には、里親による養育が逆効果をもたらすことが分かった。しかし、13歳以前に里子に出された少年については、影響が見られなかった。里親による養育は少女の成年後の犯罪には影響を与えない。思春期に施設に出された少年と少女はいずれも、家庭外に出されることの無かった少年少女に比べ、成年後の犯罪傾向が高い。13歳以前に施設に収容された子供にはそうした傾向は見られなかった。
具体的な数字は本文の導入部で以下のように説明されている。
We find that men who were placed in foster care as children are 10 percentage points (23 percent) more likely to be convicted of a crime as adults than their investigated, but never-placed, counterparts*1. For females the point estimates are not statistically different from zero. Our subsample regressions clearly show that it is boys who are placed in foster care during adolescence (age 13-18) that account for the negative effect that placement in foster care has on the adult criminality of males. The adverse effect is an increase of 26 percentage points (58 percent) of committing at least one crime as an adult*2. A null effect is found for boys placed at earlier ages and for girls placed at any age, which is good news given the generally poor outcomes one reads about in the literature on foster care.
Placement in residential care as an adolescent has adverse effects on the adult criminality of both males and females. For men the effect is 30 percentage points (67 percent)*3 and for women the effect is 15 percentage points (71 percent)*4. Once again, we find no effect of placement in residential care on adult criminality in those children who were first placed before age 13.
*1:cf. 論文のTable3のColumn(2)のFoster Care(FC)の回帰係数が0.1で、Mean dep.var.(Males)＝0.43に対する割合が23%。
*2:cf. 論文のTable3のColumn(7)のFoster Care in P3の回帰係数が0.26で、Mean dep.var.(Males)＝0.45に対する割合が58%。
*3:cf. 論文のTable4のColumn(7)のFoster Care in P3の回帰係数が0.3で、Mean dep.var.(Male)＝0.45に対する割合が67%。
*4:cf. 論文のTable4のColumn(7)のFoster Care in P3の回帰係数の女性項が0.302-0.148≒0.15で、Mean dep.var.(Female)＝0.21に対する割合が71%。
