A new study by the Harvard economists Raj Chetty and Nathaniel Hendren, when read in combination with an important study they wrote with Lawrence Katz, makes the most compelling case to date that good neighborhoods nurture success. (The Upshot has just published a package of articles and interactives on the study.)

Let me be upfront about my own reading: These two new studies are the most powerful demonstration yet that neighborhoods — their schools, community, neighbors, local amenities, economic opportunities and social norms — are a critical factor shaping your children’s outcomes. It’s an intuitive idea, although the earlier evidence for it had been surprisingly thin. As Sean Reardon, a professor of education and sociology at Stanford, said of the study, “I think it will change some of the discussion around how where children grows up matters.”

That's Justin Wolfers on this paper (PDF) by Chetty and Hendren.

Those earlier analyses grouped children who moved to a neighborhood as toddlers with those who moved in their late teens. So comparing all of the children whose parents won the lottery with all of those whose parents lost showed small effects. Yet if what matters are years of exposure to a good neighborhood — a hypothesis strongly suggested by the second of these two studies — then the effects might be very different, as those who moved as toddlers enjoyed most of their childhood in better neighborhoods, while those who moved as teens received few such benefits yet still had to deal with the disruption of moving.

Armed with this hypothesis and also newer data on the longer-run outcomes of these children, Mr. Chetty, Mr. Hendren and Mr. Katz reanalyzed the outcomes of the same families. (Full disclosure: Lawrence Katz was my Ph.D. adviser.)

And the findings are remarkable. In particular, the previous results actually hide two quite distinct findings, one positive and one negative. The children who moved when they were young enjoyed much greater economic success than similarly aged children who had not won the lottery. And the children who moved when they were older experienced no gains or perhaps worse outcomes, probably the result of a disruptive move, paired with few benefits from spending only a short time in a better neighborhood.

As Tyler Cowen notes, the biggest problem with poverty tends to be “you usually end up living near other poor people.” Or, as Judith Rich Harris wrote in her groundbreaking book The Nurture Assumption, a children's peer group may have a great influence on that child's outcomes than their parents. I first learned all this from Boyz in the Hood.

How does this square with the popular theory that general intelligence is most important to one's future outcome? I hypothesize some interaction effects between the two, with the right neighborhood being an environment most conducive to wringing all the potential from genetically inherited general intelligence. Peer emulation or peer pressure exerting an activation effect.

Whatever the reason, it's clear how complex it is to break the cycle of poverty. So many nested problems, from education to urban planning to crime, all nearly impossible to isolate.