I discovered this making a scatter with INCWAGE (y axis) and total annual hours worked (wkswork1*uhrswork) for different industries. There is a gap between 200 and 300 thousands with almost no response there. I created my own aggregate of industries and it is the same. Some graphs are included. A Histogram of the variable INCWAGE show that.
I did for 1990 and I found the same pattern.
Histogram wages year.pdf (15.8 KB)