Assuming their controls are adequate, that would still leave 90% of the wage difference between white workers and ethnic minorities, which was recently estimated to be 14%, unexplained.
This could conceivably be the product of discrimination, or of something else.
Digging out the cause of this curious gap remains hazardous.
Worse treatment by managers of minority workers may itself encourage slacking, says Philip Cohen, a sociologist at the University of Maryland.
The authors argue that this point is moot, since self-employed minority workers show similar behaviour, but the difference is not statistically significant.
A recent experimental approach, in which cashiers in French grocers’ shops were randomly assigned to more- or less-biased managers, saw greater absences and more sluggish scanning when working under the unfair bosses.
It found that eliminating manager bias would increase time spent at work by minorities by an estimated 2.5%.
Uncomfortable though the topic may be, the authors have attempted a rigorous analysis.
Denunciations came quickly, however.
Within hours of publication, Mr Hamermesh received vitriolic messages and was labelled a racist in an online forum popular among economists.
Mr Hamermesh, an avowed progressive, who refers to Donald Trump only by amusing nicknames and resigned from a post at the University of Texas over a state law permitting the open carrying of firearms, finds this unfair.
He notes that Americans work too much.
His preferred solution would not be for some groups to work more, but for others to work less.