In a distribution, the frequency of a class is replaced with a proportion or percent.

I believe the correct term to fill in the blank is relative frequency. In a relative frequency distribution, the frequency of a class is replaced with a proportion or percent. The relative frequency distribution of a data variable is a summary of the frequency proportion in a collection of non-overlapping categories.

Some of the drawbacks included air and water pollution and soil contamination that resulted in a significant deterioration of quality of life and life expectancy. Industrialization also exacerbated the separation of labor and capital.