Stepwise

There was a stepwise increase for both men and women from 1980 to 1990 and 1990 to 2000, with the largest rise coming in the second interval.

a stepwise increase here means gradually increasing each interval, or

going up uniformly by X percent every interval

since stepwise means:

The steps are similar in size, like the stairs that you climb in a building.

but the increases in women were not uniformly.

Thanks a lot!