It was developed by Max Lorenz in 1906. The Lorenz Curve (the actual distribution of income curve), is a graphical distribution of wealth, shows the proportion of income earned by any given percentage of the population.
The line at the 45º angle shows perfectly equal income distribution, while the other line shows the actual distribution of income. The further away from the diagonal, the more unequal the size of the distribution of income.
Lorenz Curve