Complex sentence: The right vertical axis is the cumulative percentage of the total number of occurrences, total cost, or total of the particular unit of measure; because the reasons are in decreasing order, the cumulative function is a concave function.
Split into simpler sentences: The right vertical axis is the cumulative percentage of the total number of occurrences, total cost, or total of the particular unit of measure. Because the reasons are in decreasing order, the cumulative function is a concave function.