Median income is the amount that divides the income distribution into two equal groups, half having income above that amount, and half having income below that amount.Mean income (average) is the amount obtained by dividing the total aggregate income of a group by the number of units in that group.sing median, rather than mean income, results in a much more accurate picture of the average income of the middle class since the data will not be skewed by gains and abnormalities in the extreme ends.