We know this, though, in aggregate, because sociologists have consistently demonstrated this with these experiments they build, where they send a bunch of applications to jobs out, equally qualified but some have white-sounding names and some have black-sounding names, and it's always disappointing, the results — always.
Lo sabemos al sumarlo porque los sociólogos lo han demostrado consistentemente con experimentos que construyeron donde mandan una cantidad de solicitudes de empleo de personas de calificaciones iguales pero algunas con apellidos blancos y otras con apellidos negros, y los resultados siempre los decepcionan, siempre.