"On average, black students earned a 1.9 GPA while their white counterparts held down an average of 3.45"

The ratio between black and white GPAs = .55

"Ogbu worked from the 1990 census data, which showed that 32.6 percent of the black households and 58 percent of the white households in Shaker had incomes of $50,000 a year or more"

The ratio between number of blacks/white making above $50k/yr = .56