When you apply the reasoning US Army used in early 20th century for today it's important to remember Flynn effect.
Using IQ level standard used in 1997, average IQ in United States in 1932 was just 80. In other words average IQ was five points below what today is called normal intelligence (IQ between 85 and 115, average 100, sd 15).
Person with IQ 80 in that era was close to 70 today (very low IQ, two standard deviations below normal, only 2 percent of population today).
Using IQ level standard used in 1997, average IQ in United States in 1932 was just 80. In other words average IQ was five points below what today is called normal intelligence (IQ between 85 and 115, average 100, sd 15).
Person with IQ 80 in that era was close to 70 today (very low IQ, two standard deviations below normal, only 2 percent of population today).