Around 1990 the national average on the math portion of the SAT began its slow but steady ascension over the national average for the verbal portion. It took only one decade for the math average to eclipse the verbal average, continuing to widen since that point. The difference is sizable and significant. The average SAT test-taker today produces a math score that is 13 points higher than their verbal score. However, this was not always the case. In fact, in the 1970s the relationship was precisely the opposite when national verbal scores routinely trumped the national math average by similar margins.
The first academic analysis of this gap was conducted by James Lech Ed.D., M.T.S. Lech posited that this gap could be "collateral damage" from the well-documented academic and social "erosion" known as dumbing-down. In other words, the SAT math questions progressively eased in difficulty over time while the verbal difficulty levels 1) remained constant, or 2) dumbed-down at much slower rates.