BEN CARSON, a celebrated neurosurgeon and unsuccessful presidential candidate, had no experience in political office or housing policy before Donald Trump nominated him to lead the Department of Housing and Urban Development (HUD). It was unclear what Dr Carson, long sceptical about government assistance and social engineering more generally, would do with an agency that funds rental-assistance schemes for the poor, only half of whom actually live in cities (despite what the department’s name suggests). The administration proposed a 13% cut in HUD funding in its first budget. Dr Carson seemed not to know how individual programmes would be affected when testifying before Congress. HUD, with its annual budget of $46bn, is a tiddler compared with other federal departments, but in several ways it is a sort of miniature version of the Trump administration.

In the nine months since he took the post, Dr Carson has stayed inconspicuous and inscrutable. The agency seems directionless. Only four of the 13 top positions, which must be confirmed by the Senate, have been filled. No nominee has been announced to be either the inspector-general or head of the policy development and research office. Eric Trump’s wedding planner runs the agency’s largest regional office, in New York. Local public-housing agencies, which actually administer the federal programmes with HUD funds, privately complain of uncertainty. Dr Carson’s most significant policy decision to date has been a two-year delay of the “small-area fair market rents” (SAFMR) rule, finalised by the Obama administration, which aimed to help voucher-holders move to better neighbourhoods. This is especially perplexing because five years of testing showed that the rule has achieved its goals while reducing expenses, which conservatives should cheer.

The rule affected the most important programme run by HUD, known formally as the Housing Choice Voucher programme and colloquially as Section 8. This helps 2.2m poor households with an average income of $13,500. Lack of funding means that only a quarter of those eligible for such assistance receive it. Los Angeles recently reopened its waiting list after a 13-year hiatus. Those lucky enough to obtain vouchers need pay only 30% of their income towards rent. The government covers the rest, but only up to what is known as the “fair market rent” (FMR)—generally the 40th percentile rent in the surrounding area. Enthusiasm for housing benefits has long been half-hearted. The federal government forgoes twice as much revenue because of the mortgage-interest deduction as it spends on subsidising rent.

Because rates are calculated across an entire metropolitan area, the algorithm is poorly suited to cities. In New York City, for example, the FMR for a one-bedroom flat is a measly $1,357. When recipients settle in poorer areas, where market rents are actually below the FMR, landlords who specialise in low-income housing reap the benefits of a guaranteed, possibly inflated, government cheque each month. Low rent ceilings, the tendency of poor families to stay in their neighbourhoods and the ability of landlords in nicer parts to refuse tenants with rental assistance all mean that the programme concentrates many recipients in racially segregated and impoverished areas—the opposite of what it was intended to do. Depressingly, the median neighbourhood poverty rate is identical for poor children, whether their families hold a voucher or not.

HUD has long been aware of this problem. An interim fix was to boost payment standards in problem areas to the 50th percentile rent, rather than the 40th. This did not improve matters. Despite the extra spending, neighbourhood poverty rates and housing quality were unchanged. The SAFMR rule, which would have taken effect on October 1st, took a different approach, requiring cities to calculate rents at the zip-code level, rather than across an entire metro area. The evidence for changing the rules is powerful. Raj Chetty, Nathaniel Hendren and Lawrence Katz, all economists, found big benefits for poor children when their families were randomly assigned vouchers allowing them to live in better neighbourhoods. Adult earnings shot up by 31%, rates of college attendance rose 32% and the incidence of single parenthood dropped by 30%.

Though HUD insists that more time is needed to study the rule, some cities have already tried it out, with promising results. In Dallas, which implemented a similar rule after a court settlement, the effects have been encouraging. Research by Robert Collinson and Peter Ganong shows that voucher-holders moved to areas with less crime, poverty and unemployment. Testing in five other areas by HUD has shown that determining rents on a zip-code basis actually decreases costs, because fewer overpayments in poor areas more than compensated for higher rents elsewhere.

The results have been similarly compelling in Baltimore, where the Baltimore Regional Housing Partnership has implemented a programme to move some residents to better neighbourhoods. (Baltimore calls them “opportunity areas”; see map.) Usually that means moving people out of the city, where decrepit terrace houses sag into the street, and into the surrounding counties. Residents benefiting from Baltimore’s programme moved from areas with a 33% poverty rate to places where it was 8%. Their children attend schools where 79% of students are proficient in reading, compared with 47% in Baltimore city schools before the move.