Using student performance data gathered from the National Assessment of Educational Progress (NAEP) in the last 50 years, Hanushek et. al has observed that the achievement gap has failed to close. By plotting standard deviations observed between the 90th-10th percentiles and the 75th-25th percentiles in socioeconomic status, the following trends were observed:

• For both comparisons, the gap in achievement has remained relatively consistent.
• When comparing free/reduced-price lunch students and students ineligible for free/reduced-price lunch, the gap in achievement has also remained relatively consistent.
• When factoring in ethnicity, the gap between African American and White students decreased.
• Students between the ages of 13 and 15 (8th grade) have made improvements in learning gains over the last 50 years, while students older than 17 (12th grade) have slowly made less gains over the same period.

Overall, Hanushek et. al posit that while achievement gaps in education has failed to close, the effect observed is closer to a relative Matthew Effect, rather than an absolute one.