Indeed, according to the Fed’s analysis of the government mortgage data from 2013, banks said credit history was the reason behind 30 percent of their denials of black borrowers. For whites, banks said it was the cause in 22.5 percent of the cases.

Still, the reasons for the high rate of denials remain murky.

The government mortgage data does not contain information that would make it possible to verify the reasons that the banks give for denying mortgages. It does not, for instance, include credit scores of borrowers, which would allow researchers to better assess the creditworthiness of the potential borrowers who were denied.

A government agency, the Consumer Financial Protection Bureau, recently introduced a rule that requires the banks to include more types of mortgage data, including credit scores, but it is not clear how much of the new data will be made public. And there will be a long wait for much of the new data; banks will have to start reporting it for loans made in 2018.

As a result, questions will continue to hang over the high denial rate for blacks and the low level of lending in neighborhoods where blacks or other minorities are the majority. And these questions were in part behind the coalition’s analysis of Baltimore, a city that has in the past suffered from redlining — the term given to policies and practices that made it very difficult for blacks to obtain mortgages or take out home loans at the same terms as whites.

These days, banks are not making many loans to blacks in Baltimore.

In 2013, 797 loans were made to blacks in the city, a seemingly tiny number considering that Baltimore’s black population totals almost 400,000. Some 2,000 loans were made to the city’s 175,000 whites.

The coalition also used census data, yielding some notable findings.

In lower-income areas of Baltimore where minorities made up 10 to 19 percent of the population, 72 percent of mortgage applications were approved. But in lower-income areas where minorities made up more than 80 percent of the population, only 59 percent of applicants were approved.

One of the chief concerns among consumer advocates is that banks have effectively written off certain neighborhoods. Lenders, for instance, may shun creditworthy borrowers in neighborhoods where blacks are the majority because they may not believe that house prices will rise by much in such areas. But if banks avoid economically challenged areas for that reason, it could make it more unlikely that house prices will rise.