The literacy test—supposedly applicable to both white and black prospective voters who couldn’t prove a certain level of education but in actuality disproportionately administered to black voters—was a classic example of one of these barriers.
Blacks may have had an unremarkable failure rate, but if (proportionally) more of them were tested, then (proportionally) more of them would have failed.
The article said (emphasis added):
Blacks may have had an unremarkable failure rate, but if (proportionally) more of them were tested, then (proportionally) more of them would have failed.